November 16, 2011

SWGTREAD response to questions submitted from the NSTC Subcommittee on 

Forensic Science Research Testing Development and Evaluation Interagency Working 

Group.

QUESTION 1

What literature exist that addresses the number of characteristics/identifying marks 

required to render a conclusion?

No literature/studies could be found which specifically addresses the number of 

characteristics and/or identifying marks necessary to render a conclusion relating to 

footwear and/or tire track evidence.

Impressions evidence practitioners agree that rendering opinions relative to footwear 

and/or tire track examinations must be based upon a combination of both class and 

individual characteristics.

“Class characteristics of footwear and tires result from repetitive, controlled processes 

that are typically mechanical, such as those used to manufacture items in quantity”.1

Although defined similarly by various authors, Bodziak describes footwear class 

characteristics as “an intentional or unavoidable characteristic that repeats during the 

manufacturing process and is shared by one or more other shoes.”2

Individual characteristics are defined by Bodziak as “individual identifying characteristics 

that result when something is randomly added to or taken away from a shoe outsole 

that either causes or contributes to making that shoe outsole unique.”3 Often referred 

to as accidental characteristics, they can include cuts, scratches, gouges, holes, cracks, 

tears caused by extreme wear, or random inclusions that may result from 

manufacturing, such as bubbles, and other items or substances subsequently introduced 

to the outsole or tread, such as rocks, chewing gum, nails, tacks or small twigs. 

Footwear and tire tread examination practitioners agree that a specific number of 

individual or random characteristics are not necessarily needed to render an opinion.

It is generally accepted that the specific number of characteristics needed to assign a 

definite positive identification depends on the quality and quantity of these accidental 

 

1 Committee on Identifying the Needs of the Forensic Sciences Community, 2009, “Strengthening Forensic Science in 

the United States – A Path Forward”, National Research Council, p. 146,

2 W.J. Bodziak. 1999. Footwear Impression Evidence–Detection, Recovery, and Examination,. Boca Raton, FL: CRC 

Press, 2nd ed., p. 329.

3 Ibid, pg 335,
characteristics and the criteria established by individual laboratories.4

According to 

Cassidy, many factors and accidental characteristics are required before a positive 

identification can be established; however, the most important are the examiner’s 

experience, the clarity of the impression, and the uniqueness of the characteristic.5

Identifications are largely subjective and are based on the examiner’s experience and on 

the number of individual, identifying characteristics in common with a known standard.6

Nause best answers the question “How many accidental characteristics are required?” 

by saying “No particular set number of accidental characteristics are required to make a 

positive identification”7 He describes several factors which must be considered before 

an opinion is reached and further states “Each case must be judged on its own merits”8 

 

4K. Inman and N. Rudin. 2001. Principles and Practice of Criminalistics. Boca Raton, FL:

CRC Press, p. 129.

5 M.J. Cassidy, 1980, “Footwear Identification”, Ottawa, Ontario, Canada, Lightning Powder, Co.. Inc (reprint). 

6 Committee on Identifying the Needs of the Forensic Sciences Community, 2009, “Strengthening Forensic Science in 

the United States – A Path Forward”, National Research Council, p. 146,

7 L.S. Nause, Forensic Tire Impression Identification, 2001, Canadian Police Research Centre, pg. 223 

8 Ibid., pg 223

QUESTION 2

What is the literature that discusses the use of statistics to support an examiner’s 

conclusion?

The majority of published material that discusses the use of statistics to support 

footwear examiner’s conclusions relates to the application of “Bayes” factor in 

European countries. The Bayesian approach is not practiced in the United States. 

The following paper presents a theoretical model to give probability estimates for the 

occurrence of individual characteristics on a shoe outsole/ shoe print. The model is not 

intended for application to casework, but it demonstrates in theory how unlikely it 

would be to duplicate the occurrence of a pattern of individual characteristics. 

Stone, R.S., Footwear Examinations: Mathematical Probabilities of Theoretical 

Individual Characteristics, Journal of Forensic Identification, 2006, 56 (4), 577-599

Abstract: The trend in the forensic sciences favors objectivity over subjectivity. Courts in 

the United States are becoming increasingly hesitant to accept the opinion of an 

examiner who states, “It’s a ‘match’ because I say it’s a ‘match’”. Objectivity, in most 

cases, is reinforced by quantification. The individual characteristics that appear on a 

shoe print or shoe impression can be quantified using two primary variables. Their 

location on the print and their configuration and orientation yield measurable, 

discriminating data values. Theoretical types of individual characteristics that are found 

on shoe prints are described and discussed, and a hypothetical model is presented with 

probability estimates applied to quantify the likelihood of occurrence of the 

characteristics. With marks or combinations of marks of reasonable complexity, the 

magnitudes of the resultant numbers, though entirely abstract and based upon 

conservative assumptions, are remarkable.

This paper provides actual casework examples of the application of the likelihood ratio 

in New Zealand and the United Kingdom.

Evett, IW, Lambert, JA, Buckleton, JS, A Bayesian approach to interpreting footwear 

marks in forensic casework, Science & Justice , 1998, 38, 241-247

Abstract: This paper describes an attempt to formalize the interpretation of footwear 

marks. First, the definitions of identification and individualization which were given by 

Kirk are discussed and formalized, then a Bayesian analysis is presented in which the 

assumptions made are clarified. The analysis is broken down into components which 

reflect different interpretative issues. Application of a formal expression for the 

likelihood ratio is then illustrated by means of examples from casework in New Zealand 

and the United Kingdom.
This paper expands on the paper mentioned directly above and outlines a more detailed 

Bayesian approach that has the intent of making a more structured and transparent 

evaluation of footwear impression evidence.

J. Skerrett, et al., A Bayesian approach for interpreting shoemark evidence in forensic 

casework: Accounting for wear features, Forensic Sci. Int. (2011), 

doi:10.1016/j.forsciint.2011.01.030

Abstract: Shoemark evidence remains a cornerstone of forensic crime investigation.

Shoemarks can be used at a crime scene to reconstruct the course of events; they can 

be used as forensic intelligence tool to establish links between crime scenes; and when 

control material is available, used to help infer the participation of given individuals to 

the commission of a crime. Nevertheless, as for most other impression evidence, the 

current process used to evaluate and report the weight of shoemark evidence is under 

extreme scrutiny. Building on previous research, this paper proposes a model to 

evaluate shoemark evidence in a more transparent manner. The model is currently 

limited to sole pattern and wear characteristics. It does not account formally for cuts 

and other accidental damages. Furthermore, it requires the acquisition of relevant 

shoemark datasets and the development of automated comparison algorithms to 

deploy its full benefits. These are not currently available. Instead, we demonstrate, 

using casework examples, that a pragmatic consideration of the various variables of the 

model allows us to already evaluate shoemark evidence in a more transparent way and 

therefore begin to address the current scientific and legal concerns.

This paper is not specific to footwear comparisons, but it presents currently used 

applications of Baye’s theorem and proposes a new approach based on an extended 

likelihood ratio.

Buckleton J.S., Triggs, C.M., Champod, C., An extended likelihood ratio framework for 

interpreting evidence, Science & Justice 2006 46 69-78 

Abstract: This paper reviews some current methods, the likelihood ratio based approach 

and the full Bayesian approach for the interpretation of evidence and discusses 

previously identified shortcomings in them. It suggests an approach based on a 

compromise-based on an extended likelihood ratio - that may combine the merits of 

logic without overstepping acceptable bounds for the forensic scientist in the 

presentation of evidence. The approach is exposed formally and takes advantage of 

inferential networks called Bayesian networks.

While not specifically addressing the use of statistics to support an examiner’s 

conclusion, this article describes an initial study to build statistical models to evaluate 

the uniqueness and evolution of the pattern of accidental features occurring on shoe 

outsoles. 

Petraco, N. D. K., et. al., Statistical Discrimination of Footwear: A Method for the 

Comparison of Accidentals on Shoe Outsoles Inspired by Facial Recognition 

Techniques, J. Forensic Sci. 2010; 55(1), 34-41
Abstract: In the field of forensic footwear examination, it is a widely held belief that 

patterns of accidental marks found on footwear and footwear impressions possess a 

high degree of ‘‘uniqueness.’’ This belief, however, has not been thoroughly studied in a 

numerical way using controlled experiments. As a result, this form of valuable physical 

evidence has been the subject of admissibility challenges. In this study, we apply 

statistical techniques used in facial pattern recognition, to a minimal set of information 

gleaned from accidental patterns. That is, in order to maximize the amount of potential 

similarity between patterns, we only use the coordinate locations of accidental marks 

(on the top portion of a footwear impression) to characterize the entire pattern. This 

allows us to numerically gauge how similar two patterns are to one another in a worstcase scenario, i.e., in the absence of a tremendous amount of information normally 

available to the footwear examiner such as accidental mark size and shape. The patterns 

were recorded from the top portion of the shoe soles (i.e., not the heel) of five shoe 

pairs. All shoes were the same make and model and all were worn by the same person 

for a period of 30 days. We found that in 20–30 dimensional principal component (PC) 

space (99.5% variance retained), patterns from the same shoe, even at different points 

in time, tended to cluster closer to each other than patterns from different shoes. 

Correct shoe identification rates using maximum likelihood linear classification analysis 

and the hold-one-out procedure ranged from 81% to 100%. Although low in variance, 

three dimensional PC plots were made and generally corroborated the findings in the 

much higher dimensional PC-space. This study is intended to be a starting point for 

future research to build statistical models on the formation and evolution of accidental 

patterns.

The following two papers are related to barefoot impressions. However, the statistical 

methods used to estimate chance match probabilities can potentially be adapted to 

footwear impression problems.

Kennedy, R. B., Pressmann I. S., Chen S., Petersen P.H., Pressman A.E., Statistical 

analysis of barefoot impressions, J Forensic Sci. 2003;48(1):55–63.

Abstract: Comparison of the shapes of barefoot impressions from an individual with 

footprints or shoes linked to a crime may be useful as a means of including or excluding 

that individual as possibly being at the scene of a crime. The question of the 

distinguishability of a person’s bare footprint arises frequently. This study indicates that 

measurements taken from the outlines of inked footprint impressions show a great 

degree of variability between donors and a great degree of similarity for multiple 

impressions taken from the same donor. The normality of the set of measurements on 

footprint outlines that we have selected for this study is confirmed. A statistical 

justification for the use of the product rule on individual statistical precisions is 

developed.

Kennedy, R.B., Chen, S., Pressmann, I.S., Yamashita, A.B., Pressman, A.E., A large-scale 

statistical analysis of barefoot impressions, J Forensic Sci. 2005;50(5):1071–9.

Abstract: In an earlier paper, outlines of footprints of persons walking normally were 

studied to determine whether different people make verifiably distinct footprints. Our 
basic null hypothesis is: given a footprint outline trace made by Subject A (Alice), then 

Subject B (Bob), a distinct person, cannot produce a footprint outline trace 

indistinguishable from that of Alice. We showed in the previous work that the 

probability of a chance match is less than 10−8. In this paper we report two new 

advances in our research. First, we establish a rigorous mathematical framework for 

calculating worst case and average chance-match probabilities. Second, we repeat the 

previous experiment to substantiate the earlier results, but with an expanded 

population sample size and a more representative and significantly bigger repeated 

sample. These improvements and a new automated tracing procedure for extracting all 

numerical measures lead to a sharpened accuracy with average chance match 

probabilities of 7.88×10−10 for a general population. In other words, the odds of a 

chance match are one in 1.27 billion.

QUESTION 3

What literature exists that measures the consistency of examiner conclusions, 

incorporating multiple examiners, with various training and experience, given the 

same sample set of known “matches” and known “non-matches” of varying quality? 

Shor, Y. & Weisner, S. (1999). A survey on the conclusions drawn on the same 

footwear marks obtained in actual cases by several experts throughout the world. 

Journal of Forensic Sciences, 44 (2), 380-384. 

A survey was conducted with two sets of shoeprints from actual crime scenes and the 

corresponding suspect's shoes. Experts from seven countries were asked to give their 

opinion on the probability that the suspect's shoe made the shoeprint impression at the 

crime scene. Each expert gave his/her opinion based on the scale used in his/her

country. The distribution of the answers is discussed in this paper.

Majamaa, H. & Ytti, A. (1996). Survey of conclusions drawn of similar footwear cases 

in various crime laboratories. Forensic Science International, 82 (1), 109-120.

This study focuses on the reporting of shoeprint cases concerning the possibility of 

various laboratories drawing different conclusions from similar cases. For this purpose, 

six sets of photographs — six fictitious crime cases — were prepared. The six cases were 

distributed to the 34 crime laboratories having registered for the European Meeting for 

Shoeprint and Toolmark Examiners. The examiners in different laboratories were asked 

to examine the cases and to draw their conclusions from each of them based on 

pattern, shape, size and the accidental characteristics marked on the photos. The 

expressions for the conclusions were selected as degrees of probability. The examiners 

were asked to follow the expressions given, even if they were not using the same 

wording in their own reports. Based on the survey, there seem to be remarkable 

variations in the conclusions of shoeprint reports drawn from identical cases in different 

crime laboratories.
Note: this study is presently unpublished, has been presented as a poster at the 

International Identification Association Educational Conference 2010 and at the 

National Institute of Justice Impression and Pattern Evidence Symposium 2010.

A study of the variability in footwear impression comparison conclusions

Kate Duffy1, Lesley Hammer2, Dr. Niamh Nic Daeid1, James Fraser1

1University of Strathclyde, Centre for Forensic Science, Glasgow, Scotland,

2Hammer Forensics, Anchorage, Alaska.

Six footwear case examples were prepared and footwear examiners were asked to 

assess each comparison based solely on the observations that were clearly identified for 

each impression. By requesting that the examiners base their conclusions on the 

Scientific Working Group on Shoe Print and Tire Track Evidence (SWGTREAD) guidelines 

it was discovered that the use of standardized terminology significantly decreased the 

variations seen within thoe results reported by certified examiners. Furthermore, it was 

determined that experienced examiners are able to interpret the findings of footwear 

comparisons more accurately than individuals with an education in forensic science, but 

limited knowledge, training or experience in this particular field. Conclusions were; it is 

advantageous for footwear examiners to interpret their findings by using a standardized 

conclusions scale, as by doing so, the variation between the conclusions drawn for 

identical cases fell within a justifiable range. The variations in the conclusions of 

trained, certified footwear examiners were smaller than those of individuals with less 

training than certified footwear examiners. This finding confirms that examiners 

performing impression evidence comparisons must be knowledgeable and adequately 

educated in this field to accurately interpret footwear impression evidence. Even when 

a standardized scale of conclusions is used when interpreting the findings of a footwear 

impression comparison, some variability in the reported conclusions still exist. Reasons 

for this inconsistency may include the experience of the examiner with this type of 

comparison or the fact that the amount of corresponding individualizing characteristics 

that constitutes a positive identification is unknown.

QUESTION 4

What is the literature that addresses the effects of examiner 

experience/training/caseload in shoeprint/tire tread examinations?

Little research exists in this area, the study below addresses the question of training and 

experience, but none were found related to caseload.

Note: this study is presently unpublished, has been presented as a poster at the 

International Identification Association Educational Conference 2010 and at the 

National Institute of Justice Impression and Pattern Evidence Symposium 2010.

A study of the variability in footwear impression comparison conclusions

Kate Duffy1, Lesley Hammer2, Dr. Niamh Nic Daeid1, James Fraser1

1University of Strathclyde, Centre for Forensic Science, Glasgow, Scotland,

2Hammer Forensics, Anchorage, Alaska.
Six footwear case examples were prepared and footwear examiners were asked to 

assess each comparison based solely on the observations that were clearly identified for 

each impression. By requesting that the examiners base their conclusions on the 

Scientific Working Group on Shoe Print and Tire Track Evidence (SWGTREAD) guidelines 

it was discovered that the use of standardized terminology significantly decreased the 

variations seen within the results reported by certified examiners. Furthermore, it was 

determined that experienced examiners are able to interpret the findings of footwear 

comparisons more accurately than individuals with an education in forensic science, but 

limited knowledge, training or experience in this particular field. Conclusions were; it is 

advantageous for footwear examiners to interpret their findings by using a standardized 

conclusions scale, as by doing so, the variation between the conclusions drawn for 

identical cases fell within a justifiable range. The variations in the conclusions of 

trained, certified footwear examiners were smaller than those of individuals with less 

training than certified footwear examiners. This finding confirms that examiners 

performing impression evidence comparisons must be knowledgeable and adequately 

educated in this field to accurately interpret footwear impression evidence. Even when 

a standardized scale of conclusions is used when interpreting the findings of a footwear 

impression comparison, some variability in the reported conclusions still exist. Reasons 

for this inconsistency may include the experience of the examiner with this type of 

comparison or the fact that the amount of corresponding individualizing characteristics 

that constitutes a positive identification is unknown.

QUESTION 5

What is the literature on the potential and actual cognitive bias in shoeprint and tire 

tread examinations?

The following literature is a partial list of articles and research on the relationship of 

cognitive bias and forensic science. The question specifically calls out shoeprint and tire

tread examinations; however, it is our contention that the relative research pertaining 

to all physical match comparisons in forensic science is applicable and relative. Many of 

the papers focus their attention on fingerprint comparisons; this is primarily due to the 

dynamics of the volume of forensic comparisons conducted and the large numbers of 

test subjects available to researchers.

On the subject of cognitive bias as it relates to footwear and tire tread examinations, we 

recognize that it exists as an avoidable and controllable facet of comparison work. 

There are two primary ways of dealing with cognitive bias as a forensic community; first 

is the robust development of standards within the community that are well supported 

with scientific research, and second is training of examiners with emphasis focused on 
defining and understanding cognitive bias and the implementation of methods and 

procedures to make forensic examinations as objective as possible.

Budowle, B. et al., A Perspective on Errors, Bias, and Interpretation in the Forensic 

Sciences and Direction for Continuing Advancement. J Forensic Sci, 54(4), 2009.

Abstract: The forensic sciences are under review more so than ever before. Such review 

is necessary and healthy and should be a continuous process. It identifies areas for 

improvement in quality practices and services. The issues surrounding error, i.e., 

measurement error, human error, contextual bias, and confirmatory bias, and 

interpretation are discussed. Infrastructure is already in place to support reliability. 

However, more definition and clarity of terms and interpretation would facilitate 

communication and understanding. Material improvement across the disciplines should 

be sought through national programs in education and training, focused on science, the 

scientific method, statistics, and ethics. To provide direction for advancing the forensic 

sciences a list of recommendations ranging from further documentation to new 

research and validation to education and to accreditation is provided for consideration. 

The list is a starting point for discussion that could foster further thought and input in 

developing an overarching strategic plan for enhancing the forensic sciences.

Busey, T. & Dror, I.E. Special abilities and vulnerabilities in forensic expertise. In A. 

McRoberts (Ed.) Friction Ridge Sourcebook. Washington DC, USA: NIJ Press. March, 

2011

Abstract: Latent print examinations are complex perceptual and cognitive tasks. 

Examiners rely on their visual systems to find similarities in pairs of prints. They then 

must compare the degree of perceived similarity against others found in previous 

examinations, and ultimately must decide whether the commonalities found between 

the prints (as well as regions of unexplainable disagreement) merit the conclusion that 

the prints either did or did not come from the same source. This process involves 

perception, similarity judgments, memory and decision making. These abilities vary 

among people, and can be improved with training and experience. They are also subject 

to potential biases and external influences. In this chapter, we draw from our expertise 

in the visual and cognitive sciences to illustrate how an understanding of the human 

mind is relevant and critical to the fingerprint domain. Such an understanding clearly 

shows the unique cognitive processes and special abilities of experts, and that these also 

entail vulnerabilities. We begin with a quick overview of what we consider to be 

foundational findings in cognitive science, and then discuss how these research areas 

have been extended to latent print examiners, both in our labs and in others.

Byrd, J.S., Confirmation bias, ethics, and mistakes in forensics. J Forensic

Identification, 2006, 56, 511–525

Charlton, D., Fraser-Mackenzie, P., & Dror, I. E., Emotional experiences and motivating 

factors associated with fingerprint analysis. J Forensic Sci, 55 (3) March, 2010. In this 

study, we investigated the emotional and motivational factors involved in fingerprint 
analysis in day-to-day routine case work and in significant and harrowing criminal 

investigations. Thematic analysis was performed on interviews with 13 experienced 

fingerprint examiners from a variety of law enforcement agencies. The data revealed 

factors relating to job satisfaction and the use of skill. Individual satisfaction related to 

catching criminals was observed; this was most notable in solving high profile, serious, 

or long-running cases. There were positive emotional effects associated with matching 

fingerprints and apparent fear of making errors. Finally, we found evidence for a need of 

cognitive closure in fingerprint examiner decision-making.

Cooley, C.M., Psychological influences and the state employed forensic examiner: How 

to elicit evidence concerning observer effect errors through cross-examination and 

discovery. Illinois Association of Criminal Defense Lawyers Newsletter Summer, 2003.

http://www.law-forensic.com/iacdl_newsletter_summer_2003.htm

Dror, I. E. Perceptual, Cognitive, and Psychological Elements Involved in Expert 

Identification, Friction Ridge Sourcebook, SWGFAST, NIJ, In Press.

http://www.ojp.usdoj.gov/nij/pubs-sum/225320.htm

Dror, I.E. et al., Decision making under time pressure: An independent test of 

sequential sampling models. Memory & Cognition 1999, 27 (4), 713-725

Abstract: Choice probability and choice response time data from a risk-taking decisionmaking task were compared with predictions made by a sequential sampling model. The 

behavioral data, consistent with the model, showed that participants were less likely to 

take an action as risk levels increased, and that time pressure did not have a uniform 

effect on choice probability. Under time pressure, participants were more conservative 

at the lower risk levels but were more prone to take risks at the higher levels of risk. This 

crossover interaction reflected a reduction of the threshold within a single decision 

strategy rather than a switching of decision strategies. Response time data, as predicted 

by the model, showed that participants took more time to make decisions at the 

moderate risk levels and that time pressure reduced response time across all risk levels, 

but particularly at the those risk levels that took longer time with no pressure. Finally, 

response time data were used to rule out the hypothesis that time pressure effects 

could be explained by a fast-guess strategy.

Dror, I.E. et al. Contextual information renders experts vulnerable to making 

erroneous identifications. Forensic Science International 156 (2006) 74–78

Abstract: We investigated whether experts can objectively focus on feature information 

in fingerprints without being misled by extraneous information, such as context. We 

took fingerprints that have previously been examined and assessed by latent print 

experts to make positive identification of suspects. Then we presented these same 

fingerprints again, to the same experts, but gave a context that suggested that they 

were a no-match, and hence the suspects could not be identified. Within this new 

context, most of the fingerprint experts made different judgments, thus contradicting 

their own previous identification decisions. Cognitive aspects involved in biometric 

identification can explain why experts are vulnerable to make erroneous identifications.
Dror, I. E. & Mnookin, J. The use of technology in human expert domains: Challenges 

and risks arising from the use of automated fingerprint identification systems in 

forensics. Law, Probability and Risk. (in press).

Dror, I.E. et al., Cognitive issues in fingerprint analysis: Inter- and intra-expert 

consistency and the effect of a ‘target’ comparison, Forensic Sci. Int. (2010), 

doi:10.1016/j.forsciint.2010.10.013

Abstract: Deciding whether two fingerprint marks originate from the same source 

requires examination and comparison of their features. Many cognitive factors play a 

major role in such information processing. In this paper we examined the consistency 

(both between-and within-experts) in the analysis of latent marks, and whether the 

presence of a ‘target’ comparison print affects this analysis. Our findings showed that 

the context of a comparison print affected analysis of the latent mark, possibly 

influencing allocation of attention, visual search, and threshold for determining a 

‘signal’. We also found that even without the context of the comparison print there was 

still a lack of consistency in analyzing latent marks. Not only was this reflected by 

inconsistency between different experts, but the same experts at different times were 

inconsistent with their own analysis. However, the characterization of these 

inconsistencies depends on the standard and definition of what constitutes inconsistent. 

Furthermore, these effects were not uniform; the lack of consistency varied across 

fingerprints and experts. We propose solutions to mediate variability in the analysis of 

friction ridge skin.

Dror, I.E. and Fraser-Mackenzie, P.A.F., Cognitive Biases in Human Perception, 

Judgment, and Decision Making: Bridging Theory and the Real World in Criminal 

Investigative Failures, Ed. Rossmo, K., Taylor & Francis, 2008.

Dror, I.E. How can Francis Bacon help forensic science? The four idols of human biases. 

Jurimetrics: The Journal of Law, Science, and Technology (in press).

Abstract: In this paper, I try to find ways to improve forensic science by identifying 

potential vulnerabilities. To this end, I use Francis Bacon’s doctrine of idols, which 

distinguishes between different types of human biases that may prevent scientific and 

objective inquiry. Bacon’s doctrine contains four sources for such biases: idola tribus

(idols of the tribe), idola specus (idols of the den or cave), idola fori (idols of the market), 

and idola theatri (idols of the theatre). While his 400-year-old doctrine does not, of 

course, perfectly match up with our current world view, it still provides a productive 

framework for examining and cataloguing some of the potential weaknesses and 

limitations in our current approach to forensic science.

Dror, I.E. Paradoxical functional degradation in human expertise. In N. Kapur, PascualLeone, & V. S. Ramachandran (Eds.) The Paradoxical Brain. Cambridge, UK: Cambridge 

University Press. (in press).

Dror, I.E., and Cole, S.A., The vision in ‘blind’ Justice: Expert perception, judgment and 

visual cognition in forensic pattern recognition, Psychonomic Bulletin & Review, in 

press.

Abstract: Many forensic disciplines require experts to judge whether two complex 

patterns are sufficiently similar to conclude that both originate from the same source. 

Studies in this area have revealed that there are a number of factors that affect 

perception and judgment and that decisions are subjective and susceptible to 
extraneous influences (such as emotional context, expectation, and motivation). Some 

studies have shown that the same expert examiner, examining the same prints but

within different contexts, may reach different and contradictory decisions. However, 

such effects are not always present; some examiners seem more susceptible to such 

influences than do others—especially when the pattern matching is “hard to call” and 

when the forensic experts are not aware that they are being observed in an 

experimental study. Studying forensic examiners can contribute to our understanding of 

expertise and decision making, as well as have implications for forensic science and 

other areas of expertise.

Dror, I.E., Charlton, D., Peron, A., Contextual information renders experts vulnerable 

to making erroneous identification, Forensic Science International, 156, 2006.

Dror, I.E., Charlton, D., Why experts make errors. Journal of Forensic identification 

56(4), 2006.

Abstract: Expert latent fingerprint examiners were presented with fingerprints taken 

from real criminal cases. Half of the prints had been previously judged as 

individualizations and the other half as exclusions. We re-presented the same prints to 

the same experts who had judged them previously, but provided biasing contextual 

information in both the individualizations and exclusions. A control set of 

individualizations and exclusions was also re-presented as part of the study. The control 

set had no biasing contextual information associated with it. Each expert examined a 

total of eight past decisions. Two-thirds of the experts made inconsistent decisions. The 

findings are discussed in terms of psychological and cognitive vulnerabilities.

Dror, I.E., Peron, A.E., Hind, S-L., Charlton, D., When emotions get the better of us: The 

effect of contextual top-down processing on matching fingerprints. Applied Cognitive 

Psychology, 19, 2005.

Summary: Twenty-seven participants made a total of 2,484 judgments whether a pair of 

fingerprints matched or not. A quarter of the trials acted as a control condition. The rest 

of the trials included top-down influences aimed at biasing the participants to find a 

match. These manipulations included emotional background stories of crimes and 

explicitly disturbing photographs from crime scenes, as well as subliminal messages. The 

data revealed that participants were affected by the top-down manipulations and as a 

result were more likely to make match judgments. However, the increased likelihood of 

making match judgments was limited to ambiguous fingerprints. The top-down 

manipulations were not able to contradict clear non-matching fingerprints. Hence, such 

contextual information actively biases the ways gaps are filled, but was not sufficient to 

override clear bottom-up information.

Dror, I.E., Rosenthal, R., Meta-analytically quantifying the reliability and biasability of 

forensic experts. J Forensic Sci, 53(4), 2008.

Abstract: In this paper we employ meta-analytic procedures and estimate effect sizes 

indexing the degree of reliability and biasability of forensic experts. The data are based 

on within-expert comparisons, whereby the same expert unknowingly makes judgments 

on the same data at different times. This allows us to take robust measurements and 

conduct analyses that compare variances within the same experts, and thus to carefully 

quantify the degree of consistency and objectivity that underlie expert performance and 
decision making. To achieve consistency, experts must be reliable, at least in the very 

basic sense that an expert makes the same decision when the same data are presented 

in the same circumstances, and thus be consistent with themselves. To achieve 

objectivity, experts must focus only on the data and ignore irrelevant information, and 

thus be unbiasable by extraneous context. The analyses show that experts are not 

totally reliable nor are they unbiasable. These findings are based on fingerprint experts 

decision making, but because this domain is so well established, they apply equally well 

(if not more) to all other less established forensic domains.

Evett, I., Evaluation and professionalism. Science and Justice 49, 2009.

Forrest, R., Context-free forensic science. Science and Justice 44(2), 2004.

Giannelli, P.C., Confirmation Bias, Criminal Justice, 22(3), 2007.

Hall, L.J. and Player, E., Will the introduction of an emotional context affect fingerprint 

analysis and decision-making? Forensic Science International, 181, 2008.

Dror, I.E. On proper research and understanding of the interplay between bias 

and decision outcomes, Forensic Science International, 191, 2009.

Hall, L.J. and Player, E., The value of practitioner research in the field of 

fingerprint analysis, Forensic Science International, 191, 2009.

Saks, M.J. Concerning L.J. Hall, E. Player, ‘‘Will the introduction of an emotional 

context affect fingerprint analysis and decision making?’’ Forensic Science 

International, 191, 2009.

Hall, L.J. Player, E. The value of practitioner research in the field of fingerprint 

analysis (2). Forensic Sci. Int. 191, 2009.

Hartl, D.L., and Fairbanks, D.J., Mud Sticks: On the Alleged Falsification of Mendel’s 

Data in Perspectives in Anecdotal, Historical and Critical Commentaries on Genetics

Eds. Crow, J.F. and Dove, W.F., Genetics Society of America, 2007.

Hasel, S, Kassin, L., On the presumption of evidentiary independence Psychological 

Science; Can Confessions Corrupt Eyewitness Identifications? 20(1), 2009

Kerstholt J.H., Paashuis R., Sjerps, M. Shoe print examinations: Effects of expectation, 

complexity and experience, Forensic Science International, 165, 2006.

Abstract: Even though trace evidence is becoming more and more important in legal 

cases, only little is known about the influence of task and context factors on 

comparative judgments. In the present study we investigated how expectations and 

complexity affect shoe print examinations and to what extent differences exist between 

beginners and experienced examiners. Twelve examiners assessed similarity between a 

shoe print and a shoe for eight different cases. For half the cases expectation was 

induced by providing additional incriminating evidence. A complex case meant that the 

print was relatively noisy, for example because the perpetrator rotated his foot. A 

simple case meant that the print was clear. The results showed that there was no effect 

of expectation and no effect of experience. Only complexity affected the examiners’ 

assessments: when the background was noisy, the acquired features received a lower 

evidential value than when the background was clear. Apparently, examiners 

compensated for the quality of the print and were more cautious in drawing conclusions 

when prints were less clear. Even though the results allow for some optimism with 
regard to the influence of expectations on shoe print examinations, it has to be taken 

into account that the Dutch procedure is supported by a formal guideline, which may 

(partly) explain the present findings.

Krane, D.E., Ford, F., Gilder, J.R., Inman, K., Jamieson, A., Koppl, R., Kornfield, I.L., 

Risinger, D.M., Rudin, N., Taylor, M.C., Thompson W.C., Sequential Unmasking: A 

Means of Minimizing Observer Effects in Forensic DNA Interpretation, J Forensic Sci

53(4), 2008. 

Wells J.D. Commentary on: Sequential unmasking: a means of minimizing 

observer effects in forensic DNA interpretation. J Forensic Sci, 54(2) 2009.

Krane, D.E., Ford, F., Gilder, J.R., Inman, K., Jamieson, A., Koppl, R., Kornfield, I.L., 

Risinger, D.M., Rudin, N., Taylor, M.C., Thompson W.C., Authors’ Response, J 

Forensic Sci, 54(2) 2009.

Ostrum B. Commentary on: Sequential unmasking: a means of minimizing 

observer effects in forensic DNA interpretation. J Forensic Sci, 54(6), 2009.

Krane, D.E., Ford, F., Gilder, J.R., Inman, K., Jamieson, A., Koppl, R., Kornfield, I.L., 

Risinger, D.M., Rudin, N., Taylor, M.C., Thompson W.C., Authors’ Response, J 

Forensic Sci, 54(6), 2009.

Langenburg, G., Champod, C., and Wertheim, P., Testing for potential contextual bias 

effects during the verification stage of the ACE-V Methodology when conducting 

fingerprint comparisons J Forensic Sci, 54(3) 2009.

Abstract: This study was conducted to assess if fingerprint specialists could be 

influenced by extraneous contextual information during a verification process. Prior to 

the experiment, participants were separated into three groups: a control group (no 

contextual information was given), a low bias group (minimal contextual information 

was given in the form of a latent print examination report prompting conclusions from 

an anonymous, but qualified, specialist), and a high bias group (an internationally 

recognized fingerprint expert provided conclusions and case information to deceive this 

group into believing that it was his case and conclusions). A similar experiment was later 

conducted with novices (laypersons with no experience in conducting fingerprint 

comparisons). Participants were aware that they were being tested and participants 

may not have de facto conducted examinations in a manner consistent with their 

normal work habits. Given these limitations, the results still showed that fingerprint 

experts are influenced by contextual information during fingerprint comparisons, but 

not towards making errors. Instead, fingerprint experts under the biasing conditions 

provided significantly fewer definitive and erroneous conclusions than the control 

group. They tended to provide opinions that were inconclusive. In contrast, the novice 

participants were more influenced by the bias conditions and did tend to make incorrect 

judgments, especially when prompted towards an incorrect response by the bias 

prompt. This was not the case with the fingerprint experts. Experience (in terms of years 

of experience in fingerprint examination) was not shown to be a significant factor for 

specialists when assessing images from the same source, but was a factor when 

assessing images from different sources. Finally significant variation was observed for 

fingerprint experts when asked to count the number of minutiae in agreement for trials 
where the images originated from the same source. The number of minutiae in 

agreement as reported by the specialist was a significant factor in whether the specialist 

claimed the images to be a definitive match.

Mankevich, A. Blind verification; Does it compromise the conformance of ACE-V 

methodology to the scientific method? Chesapeake Examiner 45(2), 2007.

Miller, Larry S., Bias among forensic document examiners: A need for procedural 

changes. J Police Science and Administration, 12(4), 1984.

Miller, Larry S., Procedural bias in forensic science examinations of human hair. Law 

and Human Behavior 11(2) 157, 1987.

Phillips V.L., Saks M.J., Peterson J.L., The application of signal detection theory to 

decision-making in forensic science. J Forensic Sci; 46(2) 2001.

Abstract: Signal Detection Theory (SDT) has come to be used in a wide variety of fields 

where noise and imperfect signals present challenges to the task of separating hits and 

correct rejections from misses and false alarms. The application of SDT helps illuminate 

and improve the quality of decision-making in those fields in a number of ways. The 

present article is designed to make SDT more accessible to forensic scientists by: (a) 

explaining what SDT is and how it works, (b) explicating the potential usefulness of SDT 

to forensic science, (c) illustrating SDT analysis using forensic science data, and (d) 

suggesting ways to gain the benefits of SDT analyses in the course of carrying out 

existing programs of quality assessment and other research on forensic science 

examinations.

Risinger, D.M., Saks, M.J. Thompson, W.C., Rosenthal, R., The Daubert/Kumho 

implications of observer effects in forensic science: Hidden problems of expectation 

and suggestion. California Law Review, 90(1) 2002.

Abstract: After the Supreme Court's decision in Kumho Tire v. Carmichael and the recent 

amendment of Federal Rule of Evidence 702, proffers of expert testimony will have to 

be found reliable for the particular application of the asserted expertise to the "task at 

hand." That is, expertise which is reliable in some global sense, which might apply to 

other cases but not to the particular application before the court, does not satisfy the 

requirements for admission. With that in mind, this article examines the phenomenon 

of "observer effects" and the vulnerability of forensic science examinations to such 

observer effects. Observer effects occur when the results of an examination are 

distorted by the context and state of the observer, including the observer's expectations 

and desires. The article reviews the findings and practices of a range of scientific fields 

concerning such observer effects and their control, with special attention to the relevant

research and theory from cognitive and social psychology. This literature establishes 

that in virtually every area of human judgment, such observer effects have a relentless 

and sometimes dramatic effect on the accuracy of results. The article then examines 

current forensic science practice in light of that research, concluding that forensic 

science practice is far behind most scientific fields in controlling for such effects, leaving 

the reliability and accuracy of many forensic science results in doubt. The article then 

suggests practical ways in which forensic science practice can be changed to reduce 
such problems, such as the adoption of blind testing regimes. Finally, the article 

analyzes the current state of the law under Kumho Tire and Rule 702, concluding that 

the results of forensic science examinations are in danger of being excluded if their 

reliability continues to be undermined by the failure to control observer effects.

Saks, M.J., Risinger, D.M., Rosenthal, R., Thompson, W.C., Context effects in forensic 

science: A review and application of the science of science to crime laboratory practice 

in the United States. Science & Justice, 43(2), 2003.

Schiffer B., Champod C., The potential (negative) influence of observational biases at 

the analysis stage of fingermark individualization. Forensic Sci Int,167, 2007.

Stacey, R.M., A report on the erroneous fingerprint individualization in the Madrid 

train bombing case. Journal of Forensic Identification, 54, 2004.

Thompson WC. A sociological perspective on the science of forensic DNA testing. UC 

Davis Law Rev, 30(4), 1997.

Thompson, W.C. and Cole, S.A., Psychological aspects of forensic identification 

evidence. In M. Costanzo, D. Krauss & K. Pezdek (Eds.) Expert Psychological Testimony 

for the Courts. New York: Lawrence Erlbaum & Associates. 2007.

Thompson, W.C. and Ford, S., The meaning of a match: Sources of ambiguity in the 

interpretation of DNA prints. In J. Farley & J. Harrington (Eds.) Forensic DNA 

Technology. New York: CRC Press, Inc., 1991.

Thompson, W.C., Accepting Lower Standards: The National Research Council’s Second 

Report on Forensic DNA Evidence. Jurimetrics 37(4), 1997.

Thompson, W.C., Observer Effects, Context Effects and Confirmation Bias in Forensic 

Science in Wiley Encyclopedia of Forensic Science, Eds. Jamieson, A., and Moenssens, 

A., John Wiley & Sons, 2009.

Thompson, W.C., Painting the target around the matching profile: the Texas 

sharpshooter fallacy in forensic DNA interpretation, Law Probability and Risk, 2009

Thompson, W.C., Subjective interpretation, laboratory error and the value of DNA 

evidence: Three case studies. Genetica 96, 1995.

Thomson M.A., Bias and quality control in forensic science; a cause for concern. J 

Forensic Sci, 10(3), 1974.

USDOJ OIJ, A review of the FBI’s handling of the Brandon Mayfield Case, 2006.

Vokey, J., Tangen, J., & Cole, S., On the preliminary psychophysics of fingerprint 

identification. Quarterly Journal of Experimental Psychology, 62(5), 2009

Whitman, G., Koppl, R., Institutional Bias in Forensic Science. In Press??

QUESTION 6

What literature exists that investigates the effects of environmental conditions on 

shoeprint/tire treads?

No citations are available that specifically answer this question.

What is the literature that documents the formation of individual characteristics 

amongst a group of people wearing the same shoe for the same period of time?
Hamburg, C. & Banks, R. (2010, August). Evaluation of the random nature of acquired 

marks on footwear outsoles [PowerPoint slides]. Presentation conducted at the 

Impression and Pattern Evidence Symposium, Clearwater Beach, FL. Retrieved from 

http://projects.nfstc.org/ipes/presentations/Hamburg_random-acquired-marks.pdf

The individualization of a footwear impression is based on the postulate that 

“accidental” marks on outsoles acquired through wear are random. This project tests 

that assumption by evaluating the marks acquired on multiple pairs of shoes during 

normal wear while attempting to control certain variables that include outsole design, 

wearer, travel paths, and length of wear. This project is a long-term evaluation of an 

entire outsole of modern material and design typically seen in casework. Travel paths

were essentially reproduced for each pair of shoes by careful documentation of the 

participants’ daily activities along with the use of a pedometer to attempt to duplicate 

the number of steps taken. Test impressions were taken from each pair of shoes prior to 

the start of the project and at each predetermined interval. Four pairs of shoes were 

worn, 2 for each participant. All right shoes and all left shoes were compared to each 

other. No acquired marks were found to repeat.

Adair, T. W., Lemay, J., McDonald, A., Shaw, R. & Tewes, R. (2007). The Mount Bierstadt 

study: An experiment in unique damage formation in footwear. Journal of Forensic 

Identification, 57 (2), 199-205.

Randomly formed damage on footwear outsoles has appropriately been used to 

compare crime scene impressions to the known shoes of suspects, witnesses, and

victims. In this study, the authors wore new, identical boots (two pairs) during a sevenmile hike. The authors attempted to control the major variables except the manner in 

which the outsole of the boot made contact with the ground. The results of this 

experiment support the use of these marks for the individualization of footwear and 

confirm their random formation through the use of the shoe by the wearer.

Wyatt, J. M., Duncan, K., Trimpe, M. A. (2005). Aging of shoes and its effect on shoeprint 

impressions. Journal of Forensic Identification, 55(2), 181-188.

This research studied the change in the outsole patterns over a given amount of time in 

order to investigate what is to be expected in a two-month delay in the collection of 

known samples from a suspect. The study compared the class characteristics, wear 

patterns and individual characteristics of 54 different shoe outsoles before and after a 

two-month time lapse. The research concluded that an identification is still possible 

even if a known shoe is collected two months after the crime occurred.

Fruchtenicht , T.L., Herzig, W.P., 2 & Blackledge, R.D. (2002). The discrimination of twodimensional military boot impressions based on wear patterns. Science & Justice, 42 (2), 

97-104.
A study was undertaken to determine the discrimination value of wear patterns in the 

comparison of two-dimensional footwear impressions with questioned shoes. In order 

to isolate the influence on wear caused by individual differences in weight, bone 

structure, and walking styles, only right foot, size 10, military combat boots worn by US 

marines were studied. A commercial footwear impression kit featuring a chemically 

infused pad and sensitized paper was used for boot impression acquisition. Feature 

measurement was accomplished with an image analysis system to acquire the twodimensional impressions as files, and then using a commercial marker-measurement 

system. A total of 127 different right boot impressions were acquired, scanned, 

measured, and measurement values entered into the database. The power of the 

developed metrics to discriminate between outsole impression patterns was evaluated 

in a blind challenge experiment. The system analyst was provided with 26 coded outsole 

impression sheets as “unknowns”, of these, 22 had been previously entered in the 

database and four were outside samples. No false matches were made, and of all the 

non-matching images in only one instance did all of measurements fall within the 0.10 

cm match criteria selected by the system operator.

Toso, B. & Girod A. (1997, September). Evolution of random characteristics (appearance 

and disappearance). Presentation conducted at the First European Meeting of Forensic 

Science, Lausanne, Switzerland.

This research was conducted to analyze the appearance and disappearance of random 

characteristics with respect to size and location on twelve pairs of shoe soles. These 

shoes were worn for a period of fifty days. Test impressions were made from each shoe 

at ten-day intervals to track the appearance and disappearance of the random 

characteristics observed on the shoes. The following conclusions were reached at the 

end of this study regarding random characteristics: (1) those characteristics which 

appear frequently on the sole tend to disappear rapidly, (2) the appearance and 

disappearance of these characteristics is gradual with time, (3) these characteristics are 

more likely to appear than to disappear, (4) small characteristics disappear more 

frequently and faster than large random characteristics, and (5) the majority of the 

characteristics that were present at ten days were still present at 50 days and their 

location and size were recognizable.

QUESTION 7

What is the literature that investigates the transfer of identifying features from sole or 

tread to impression medium across differing substrates?

Bodziak, W. J. (2008). Tire tread and tire track evidence: Recovery and forensic 

examination. Documenting and recovering tire impression evidence (pp. 45-48). Boca 

Raton, FL: CRC Press. 
Bodziak, W. J. (2000). Footwear impression evidence: Detection, recovery and 

examination, 2nd edition. Awareness, detection, and treatment of footwear impression 

evidence (pp. 7-24). Boca Raton, FL: CRC Press.

QUESTION 8

What is the literature that investigates the development of defects/individualizing 

characteristics on different sole or tread materials?

Bodziak, W. J. (2000). Footwear impression evidence: Detection, recovery and 

examination, 2nd edition. Awareness, detection, and treatment of footwear impression 

evidence (pp. 7-24). Boca Raton, FL: CRC Press.

Toso, B. & Girod A. (1997, September). Evolution of random characteristics (appearance 

and disappearance). Presentation conducted at the First European Meeting of Forensic 

Science, Lausanne, Switzerland.

This research was conducted to analyze the appearance and disappearance of random 

characteristics with respect to size and location on twelve pairs of shoe soles. These 

shoes were worn for a period of fifty days. Test impressions were made from each shoe 

at ten-day intervals to track the appearance and disappearance of the random 

characteristics observed on the shoes. The following conclusions were reached at the 

end of this study regarding random characteristics: (1) those characteristics which 

appear frequently on the sole tend to disappear rapidly, (2) the appearance and 

disappearance of these characteristics is gradual with time, (3) these characteristics are 

more likely to appear than to disappear, (4) small characteristics disappear more 

frequently and faster than large random characteristics, and (5) the majority of the 

characteristics that were present at ten days were still present at 50 days and their 

location and size were recognizable.

QUESTION 9

What literature exists that describes the automated systems in shoeprint/tire tread 

examinations?

What literature exists that addresses the accuracy and validity of automated systems 

in shoeprint/tire tread examinations?

What literature exists that addresses the effectiveness of human examiners and 

automated systems used in conjunction to render a conclusion in shoeprint/tire tread 

examinations?

Note:

Automated systems used by footwear and tire track analysts are utilized for the 
collection of information that may lead to a make and model determination.

Automated systems are not currently utilized to compare the unique features of a 

questioned impression from a scene to the unique features of a suspect’s shoe or tire. 

All currently available databases for shoes or tires require the manual input of 

information (shape codes or measurements) by the examiner, and manual inspection of 

the results for an identification of make and model to occur.

Various forensic laboratories (FBI, other countries) may have their own collection of 

known shoes or tires in a database, which they use for searches. These databases may 

also include collections of scene impressions which can be searched.

Footwear

A commercially available footwear database is available for use by forensic laboratories.

Questioned tread designs can be searched in an attempt to determine the make and 

model of footwear that made the impression. The results of a make and model search 

are provided to an agency as an investigative lead. Shoeprint Image Capture and 

Retrieval (SICAR) is sold by the company Foster & Freeman is a computer software 

program that can be used to perform searches of a database of known footwear 

(SOLEMATE) and other outsoles input by laboratory personnel. This database is not a 

comprehensive database of all footwear sold, and only represents a fraction of those 

sold worldwide. Searches are performed by the manual “coding” of a questioned 

impression utilizing its apparent tread design shapes and orientations. A list of “hits” 

will result, however a manual comparison is necessary before any correlation can be 

made.

Crimeshoe.com is an internet service of Foster & Freeman where you pay for them to 

search your questioned impression and provide the possible results.

TreadMark is another commercially available footwear database by the company CSI 

Equipment Ltd. (United Kingdom). It reportedly provides for a central database of 

footmarks left at crime scenes, and images of footwear taken from prisoners. The 

database is accessible to all those who have an interest in footwear evidence from their 

own personal computer. Calibrated images of footmarks can be entered by crime scene 

investigators. According to the manufacturer, the custody officers have an easy means 

of taking images of the soles of the shoes taken from suspects. Footwear expert 

examiners can process the images – identifying the pattern code, marking up damage 

and searching the database to make scene to scene and scene to suspect links. Using 

the TreadMark interface these links are added to a ‘Crime Series’ which in turn form the 

basis of intelligence reports.
Tire

Foster & Freeman also sells TreadMate. This is a reference collection containing details 

of over 8,500 vehicle tires (not a comprehensive collection). It may be used as a standalone system or with SICAR, the company’s shoe print and tire mark evidence 

management system

Tread Assistant was a searchable database containing images of tire tread designs - This 

database was discontinued in 2010.

Tire Stance: 

There was previously a database available for searching vehicle tire stance 

measurements. Jato Dynamics developed a web-based search program which provided 

web access to vehicle stance data which was periodically updated. Jato released 

TirePrint.com in 2003 and sold subscriptions until 2009 when they discontinued the 

service. Now, there is at least one online resource, Canadian Transport’s Canadian 

Vehicle Specification Program, that has vehicle stance measurements as a content of a 

database. The program is free and updated at least twice a year. The program has the

three most used measurements, front track, rear track and wheelbase. The current 

version contains vehicle data from 1971 to 2011.

Literature:

What literature exists that describes the automated systems in shoeprint/tire tread 

examinations? 

Bodziak, William J. (2000) Footwear Impression Evidence Detection, Recovery and 

Examination, pg 284

The author describes some databases that have been utilized by forensic examiners for 

footwear evidence.

Bodziak, William J. (2008) Tire Tread and Tire Track Evidence Recovery and Forensic 

Examination, 270-286

The author describes the databases that have been utilized by forensic examiners for 

tire tread and tire track evidence.

Robin Bowen; Jessica Schneider (2007) Forensic Databases: Paint, Shoe Prints, and 

Beyond. National Institute of Justice Journal Issue: 58, 34-38

Contains information about available databases: “... TreadMark is a commercial product 
that uses four parameters--pattern, size, damage, and wear--in order to identify 

individual outsole impressions. These are then compared with shoe-print data from 

suspects in custody and crime scenes. The SoleMate database contains information on 

over 12,000 sports, work, and casual shoes (manufacturer, date of market release, an 

image or offset print of the sole, and pictorial images of the uppers). TreadMate 

contains information on more than 5,000 vehicle tires and tire tread patterns.”

Information is provided on how each of the forensic databases work and the 

organization that manages it. 

Keijzer, J.; Geradts, Z. ; Keereweer, I. (1995) Nationwide Classification System for Shoe 

Outsoles Designs Journal of Forensic Identification, Volume: 45 Issue:1, 30-37

In the Netherlands, a project was been initiated to develop a nationwide classification 

system in which data on footwear outsole designs and footwear impressions can be 

stored. When completed, the database was to be made available to police districts who 

can communicate with each other by a wide area network called PODACS (Police Data 

Communication System). The database consists of three parts: (1) outsole shoe designs 

which can be purchased in shops in the Netherlands; (2) shoe outsole designs from 

suspects; and (3) images of footwear impressions found at crime scenes. Shoe 

classification systems in other countries are also noted. 

Bolhouse, R.J. (1984) The identification of vehicles from wheelbase and tire stance 

measurements. Identification News, 34 (6), 5 - 6

and

Bolhouse R.J., and Nause, L.A., (1990) Tires and computers, R.C.M.P. Gazette (Cand.), 

52:1, 1 - 11.

The authors describe a searchable database containing tire track (stance) measurements 

that was a collaboration of the Michigan State Police and the RCMP. (Note: This type of 

information was more recently available using TirePrint.com, however that has been 

discontinued)

Mikkonen, S., Suominen, V., Heinonen, P. (1996) Use of footwear impressions in crime 

scene investigations assisted by computerised footwear collection system,

Forensic Sci. Intl, Volume 82, Issue 1, 67-79

(Finland) Crime scene footwear classification systems utilized to look for possible 

suspects, to get models and brand names for crime scene impressions and to link crime 

scenes. In this work a computerized footwear classification system was presented. The 

classification coding of the system was been designed especially for partial footwear 

impressions which are the most typical in crime scenes. The system is flexible because it 

is possible to agree within a crime scene investigation unit the way in which the system 

is to be applied. The accurate classification coding is propounded by the fact that only a 

few experienced users are needed to perform the classification and data storage and all 

police officers returning from crime scenes are able to perform searches very easily. The 

crime scene investigation unit of the Turku police tested the system for a period of 1.5 

years. The system has proved to be of valuable assistance in investigation when several 
of the hints lead to early solving of a crime. Practical experiences are described.

AlGarni, G., Hamiane, M., (2008) A novel technique for automatic shoeprint image 

retrieval Forensic Science International, Volume 181, Issues 1-3, 10-14

(Saudi Arabia) Recent developments in forensic science have resulted in large numbers 

of scene of crime images being collected for recording and analysis. Shoeprint images 

are no exception. In fact, these have recently been of great interest to police and 

forensic scientists as footwear evidence is now treated in the same manner as 

fingerprint and DNA evidence. Traditional approaches to shoeprint representations 

attempt to classify shoeprint images based on a number of possible patterns. Such 

approaches are difficult to implement in an automatic fashion without the intervention 

of a forensic specialist. This paper presents a robust algorithm for shoeprint matching 

based on Hu’s moment invariants. It is shown that decreasing the resolution of images 

does not have a significant effect on the performance of the algorithm. It is also shown 

that the optimal performance of the proposed system is attained for images rotated by 

any angle.

Geradts, Z., Keijzer, J. (1996) The image-database REBEZO for shoeprints with 

developments on automatic classification of shoe outsole designs

Forensic Science International, Volume 82, Issue 1, 21-31

(Netherlands) A database for footwear outsole designs developed on a PC. The database 

consists of three files: shoes of suspects, shoeprints from the scene of crime and shoes 

available from the shops. For REBEZO an algorithm is implemented for the automatic 

classification of outsole patterns. The algorithm first segments the shoe profiles in 

different profiles. The Fourier-features are calculated for those profiles. The best Fourier 

features are selected and are classified with a neural network. By using this algorithm 

many different shapes can be recognized. Integrating the results of the invariant 

moments in the neural network will give better results.

Natarajan, N., Ranjit, G.M., (2005) Computer assisted analysis of footprint geometry, 

Journal of Forensic Identification, Volume: 55, Issue: 4, 489-498

The authors describe the mechanics of using each of the following geometric tools: 

straight line/slanting line tools, the rectangle/square tool, and the ellipse/circle tool. The 

use of the software to superimpose two footprints for comparison is also described. 

Various measurements of two-dimensional footprints (foot length, ball width, intertoe 

separation, angles subtended by the center of the toes to the axis, etc.) can be 

calculated faster and more accurately with appropriate computer software than with 

the tools of manual measurement (ruler, protractor, etc.). Although not tested in the 

current study, other software similar to Adobe Pagemaker, such as QuarkXpress and 

CorelDraw, can also be used to calculate and compare footprint dimensions

What literature exists that addresses the accuracy and validity of automated systems in 

shoeprint/tire tread examinations?

What literature exists that addresses the accuracy and validity of automated systems 
in shoeprint/tire tread examinations?

Bodziak, William J. (2008) Tire Tread and Tire Track Evidence Recovery and Forensic 

Examination, 270-286

The author describes the databases that have been utilized by forensic examiners for 

tire tread and tire track evidence, and describes the use and variability that can be 

obtained depending on how the data entry is performed.

Mikkonen, S., Astikainen, T. (1994) Databased classification system for shoe sole 

patterns: Identification of partial footwear impression found at a scene of crime 

Journal of Forensic Sciences, Volume: 39 Issue:5, 1227-1236

Finland – An evaluation of a database made in-house. Sole designs are stored with 

shoe information (brand name, size, style, material, etc.), pattern types, and certain 

features on shoe soles or in footwear impressions, and they are used as searching 

criteria. There are two different classification code systems in the database. Preliminary 

classification is a very broad classification, and it is meant for shoe-sole pattern designs 

and full shoe-sole impressions; its classification codes are based on defined basic shapes 

and certain principles that facilitate storing partial footwear impressions, shoe-sole 

designs that identify partial impressions, and the elimination of interpretation error 

while classifying. They determined that the user-friendly software made the 

classification easy and searches rapid and effective. Until now the system has been 

tested in laboratory conditions. It has recently been installed in a local police unit for 

pilot testing. According to the experiences collected, the feature classification seems to 

be flexible, because it permits a feature to be composed of the defined basic shapes and 

certain definitions. The user must only follow the simple principles and order of the 

coding while classifying. The classification could also be used both at a very accurate 

level and a lower level. Because the coding is started from the center of the feature 

outward, it was determined to be easy to find an agreement at the local level with 

sufficient accuracy. 

Lin, G., Elmes, G., Walnoha, M., and Chen, X. (2009) Developing a spatial-temporal 

method for the geographic investigation of shoeprint evidence Journal of Forensic 

Sciences Volume 54, Issue 1, 152–158 

This article examines the potential of a spatial-temporal method for analysis of forensic 

shoeprint data. The large volume of shoeprint evidence recovered at crime scenes 

results in varied success in matching a print to a known shoe type and subsequently 

linking sets of matched prints to suspected offenders. Unlike DNA and fingerprint data, a 

major challenge is to reduce the uncertainty in linking sets of matched shoeprints to a 

suspected serial offender. Shoeprint data for 2004 were imported from the Greater 

London Metropolitan Area Bigfoot database into a geographic information system, and 

a spatial-temporal algorithm developed for this project. The results show that by using 

distance and time constraints interactively, the number of candidate shoeprints that can 

implicate one or few suspects can be substantially reduced. It concludes that the use of 

space-time and other ancillary information within a geographic information system can 
be quite helpful for forensic investigation.

Hannigan, T.J., Fleury, L.M., Reilly, R.B., O’Mullane, ., B.A. deChazal P., (2006) Survey 

of 1276 shoeprint impressions and development of an automatic shoeprint pattern 

matching facility Science & Justice, Volume 46, Issue 2, 79-89

The study included an effort to make the use of databases for assessing the strength of 

matching pattern evidence easier and more widespread by developing a fully automatic 

shoeprint processing system using scanned images. The test impressions were made on 

paper under ideal conditions. The result was that the system could sort images, but did 

not sort database images as successfully in response to partial prints as when processing 

full prints. They concluded that to have practical application, a system must be able to 

deal with photographs of crime scene impressions and further work would need to be 

done to accomplish that.

T.J. Napier (2002) Scene linking using footwear mark databases Science & Justice, 

Volume 42, Issue 1, 39-43

Analysis of crime scene data which includes footwear pattern, time and place was 

evaluated as to its usefulness in linking crime scenes. They determined that for 

footwear databases to provide useful intelligence in that regard, they need to contain 

very precise pattern coding to be highly discriminating. They also need to be able to 

analyze incidents from a geographical and time perspective in relation to footwear 

patterns.

Belser, Ch., Ineichen, M., Pfefferli, P. (1996) Evaluation of the ISAS system after two 

years of practical experience in forensic police work Forensic Science International, 

Volume 82, Issue 1, 53-58

(Switzerland) ISAS is an intelligent system for the administration of footwear 

impressions and reference-shoesoles, which had been in practical use with the Forensic 

Science Division of the Zurich Cantonal Police for two years at the time of writing. It is a 

powerful, efficient and user-friendly system, developed in co-operation with an external 

picture processing specialist, that can comfortably handle a database of 10,000 and plus 

images. Even inexperienced users are able to find a reference-sole in a short time. The 

system has proved to be an efficient tool in investigation assistance and crime scene 

linking.

What literature exists that addresses the effectiveness of human examiners and 

automated systems used in conjunction to render a conclusion in shoeprint/tire tread 

examinations?

Geradts, Z., Bijhold, J. (2002) Content based information retrieval in forensic image 

databases Journal of Forensic Sciences Volume: 47 Issue:2, 285-292

This research assesses how the various algorithms for correlation and image matching 

are applicable in forensic science. First, an overview is provided of current research and 

applications, followed by an application of these methods to several forensic databases, 
each focusing on a different method of matching images. These databases are tool 

marks, shoeprints, cartridge cases, and drugs/pills. In the literature, databases are 

divided into different generations. This research focuses on second generation visual 

information systems. In these systems, there are different ways of searching in the 

database . The user can search in the database on features such as texture, shapes, and 

color distribution. The features can be combined with text strings in the database. With 

this method, the user can search for a certain group of cases in a forensic database and 

compare the images with features of the images. Most current research focuses on 

finding features in images, indexing a database in an efficient manner, and the manmachine interface. A sketch generated by the user will be compared with a database of 

images. Whether this framework will actually be used very much will depend on the 

market. In future databases, more powerful methods that require parallel processing 

can be used. The authors concluded that it may be possible to automate the 

classification of the outsole design as long as the classification matrix is not too 

complicated. They also conclude that searching in the databases on content is still a 

difficult task, since shoeprints are often blurred. This requires the examiner to do much 

of this work manually. 

Ashley, W. (1996) What shoe was that? The use of computerised image database to 

assist in identification, Forensic Science International, Volume 82, Issue 1, 7-20

(Australia) The use of a computerized (digital image-based) reference system for the 

capture, storage and retrieval of shoe soles and uppers with the ability to give 

information to the investigator in relation to the brand and model of shoe responsible 

for impressions located at crime scenes. The success of the system described was due to 

the diversity and simplicity of the classification codes, coupled with the ability to search 

part or all of a shoe sole area. Determined to have discriminating power with the use of 

icons and ‘click on’ features, making the system useful when classifying and searching 

for shoes, thus reducing the possibility of interpretation error.

Other:

Girod, A., (1996) Computerized classification of the shoeprints of burglar’s soles. 

Forensic Sci. Intl., 82(1)

Description of the system created at the forensic technical laboratory in Neuchâtel, 

Switzerland, offering a means of classification concerning the standards of the 

shoeprints of burglars' soles. This classification system was created using the data 

processing program FileMaker Pro 2.1 of Macintosh. It had been established in 

Neuchâtel for 4 years and contains over 1500 reference files. During this period of time 

it has been possible to identify four times as many burglars through shoeprints than 

with fingerprints.

Smith, J., (2007) Image enhancement and Adobe Photoshop: Using calculations to 

extract image detail, Journal of Forensic Identification Volume: 57 Issue: 4, 493 to 505

This article presents step-by-step instructions, along with a case example, of how to use

Adobe Photoshop to clarify image details while reducing distracting background 
patterns during forensic print analysis.

Napier, T.J. (2002) Scene linking using footwear mark databases. Science & Justice, 42 

(1), 39 - 43. 

(United Kingdom) Scene linking using footwear mark databases.

QUESTION 10

What is the literature on error rates in shoeprint/tire tread examinations?

Peterson, J. L., Markham, P, “Crime Lab Proficiency Testing Results, 1978-1991, II: 

Resolving Questions of Common Origin,” Journal of Forensic Sciences, JFSCA, Vol. 40, 

No. 6, November 1995, pp. 1009-1029.

Proficiency tests have been used by crime laboratories since the mid-1970s as a quality 

control mechanism to measure and monitor the proficiency of their examiners. These 

proficiency tests are created by an outside entity and purchased by crime laboratories. 

This research examined proficiency test results from the period of 1978-1991 in order to 

study the proficiency of laboratories in determining common origin of various physical 

evidence samples. Proficiency tests for footwear were started in 1985 therefore this 

study looked at the seven test results from 1985-1991. From a total of 1745 

comparisons, 87% of the comparisons agreed with target values and only 0.7% did not 

while 12% were inconclusive. Overall, the study reported that footwear impression 

comparisons were one area in which laboratories performed the best. The article stated 

that while the rates of successful responses were lower than some of the other 

disciplines it had the second lowest rate of improper responses.

Collaborative Testing Services Inc., CTS Statement on the Use of Proficiency Testing 

Data for Error rate Determination, March 30, 2010, www.collaborativetesting.com. 

Collaborative Testing Services, Inc. (CTS) provides proficiency tests to crime laboratories 

on a fee for test basis. In a statement released in March 2010, CTS acknowledges the 

attempt by some to use their proficiency tests as a mechanism to calculate error rates 

but states that its tests can not and should not be used for such purposes. In this 

statement CTS explains that demographic information about the participants is not 

routinely gathered and that the participants include a wide margin of experience. CTS 

also states that they have no control over how an agency might use one of its tests. An 

agency could be using the test as a proficiency test for accreditation requirements or for 

training new examiners. Also, CTS points out that they do not record “correct” and 

“incorrect” responses, only whether the response agrees or disagrees with the 

consensus of the conclusions received. Also, the tests are designed to meet 

accreditation requirements and are not intended to simulate a real-world environment. 

For all of these reasons CTS claims that its proficiency tests can not be used as a true 

indication of the error rates in each discipline tested.
H. Majamaa, Y. Anja, “Survey of the Conclusions Drawn of Similar Footwear Cases in 

Various Crime Laboratories,” Forensic Science International, 1995, 82: 109-120.

This study examined the conclusions drawn between various footwear examiners in a 

variety of laboratories in 20 European counties. The study provided 6 tests to 34 

laboratories in which they received 33 responses. The objective of the study was to 

examine any variability between conclusions between examiners. The study found wide 

variations in the conclusions drawn by different examiners. The major limitation of this 

study were differences in reporting styles and reporting criteria of different laboratories.

*Caution should be exercised when trying to use this study to gather information about 

the conclusions drawn by footwear examiners in the United States. European examiners 

use different wording in their conclusions than those in the United States. An additional 

study was performed in the United States by Duffy, K. et. al., that found conclusions to 

have very little variability. This study has not yet been published.

QUESTION 11

What is the literature that addresses the feasibility and reliability of partial print 

comparisons (i.e. situations where some of the sole pattern may be present with 

individual detail, but there is insufficient detail to compare class characteristics)?

Impression evidence, is by it’s nature almost exclusively only a partial print of the item 

that was impressed on the surface. A footwear or tire impression which exhibits

sufficient clarity that individual detail is visible will have some degree of class 

characteristic also visible, or be so minute as to preclude a comparison from being made 

or a conclusion reached. The main factor that must be considered when doing a 

comparison of any evidence is clarity. There is a direct inverse relationship between 

quality ( clarity ) and quantity , in that if clarity is low, a greater quantity of detail is 

necessary to reach a conclusion than if clarity is high.

Petraco, Nicholas.et al., Statistical Discrimination of Footwear: A Method for the 

Comparison of Accidentals on Shoe Outsoles Inspired by Facial Recognition 

Techniques Journal of Forensic Sciences, Vol. 55, No. 1(Jan 2010), p. 34-41.

Authors applied statistical techniques used in facial pattern recognition to a minimal set 

of information gleaned from accidental patterns , using only the coordinate location of 

accidental marks to characterize the entire pattern. They numerically gauged the 

similarity of the two patterns one to another in a worst-case scenario. They used only a 

partial portion of the shoes studied, all of the same make, model, and worn by the same 

person for the same amount of time. Out of the 135 accidental patterns recorded for 

nine shoes , 116 contained at least one accidental mark. This study used only a tiny

amount of the information typically available to a footwear examiner , and yet using 

PCA it was found that of the 32 PC’s described 99.5 % of the total variance of the data 

set.
Adair, T. W., Lemay, J., McDonald, A.,Shaw, R., Tewes,R. The Mount Bierstadt Study: 

An Experiment in Unique Damage Formation in Footwear. Journal of Forensic 

Identification 57,2 ( Mar/Apr 2007) 199-205

The authors obtained new boots, made test impressions of them, then wore the boots 

over the same path at the same time on a hike, with each person wearing two pairs of 

boots during the experiment. The of the 38 elements of the boots were given specific 

address locations and individual characteristics in each location were recorded.

Comparisons conducted between all of the outsoles at each of these address locations, 

found that there were no corresponding marks at any locations, supporting the 

reliability of partial impression comparisons. 

Cassidy, Michael J., Footwear Identification Government of Canada Press, 1987

The author conducted a research project involving 194 boots, specifically the heels only. 

The boots were worn in the same geographical area ( RCMP Training Academy) 

examining wear and accidental (individual) characteristics, to determine the possibility 

of accidental characteristics reoccurring in the same place on other shoes, and the 

incidence of general wear being repeated.

Approximately 10,000 examinations were conducted. The author concluded that each 

characteristic must be weighed on its own individual merits, and that how the 

characteristic is individually shaped and how accurately they are recorded is more 

important than the size of the characteristic.

QUESTION 12

What is the literature that describes the rarity of class characteristics and uniqueness 

of individual characteristics in shoeprints/tire treads?

What published databases exist that describe the frequency statistics of various 

shoeprint/tire tread patterns?

Existing literature describing the rarity of class characteristics and uniqueness of 

individual characteristics is described below. It should be noted that the term class 

characteristics encompasses a group of characteristics that includes but is not limited to 

shoe outsole/tire tread design.

Numerous attempts have been made at producing databases of shoe outsole and tire 

tread patterns. These databases have not attempted to catalogue the frequency of 

occurrence of each pattern in the population; rather, they have attempted to represent 

examples of as many patterns as possible to assist the examiner when determining the 

makes and models that could have created an unknown impression.

There are no known databases that describe the frequency of occurrence for shoe 

outsole/tire tread patterns. A database project of this type would present significant 

challenges in terms of characterizing the entire shoe/tire population. At present, there is 
no reasonable means of tracking ongoing production statistics for every manufacturer, 

make, and model of shoe/tire. In addition, because the length of time shoes and tires 

are retained and used is highly variable and because these items are often transported 

over long distances, it is difficult to determine how long a particular shoe/tire might be 

in circulation in a given population. Once the manufacturer of a particular shoe or tire is 

known, it is sometimes possible to obtain information on the production and 

distribution of a specific type of item by contacting the manufacturer. 

Adair, T.W., Lemay, J., McDonald, A., Shaw, R., Tewes, R.; The Mount Bierstadt Study: 

An Experiment in Unique Damage Formation in Footwear, Journal of Forensic 

Identification, 57(2), 199-205

In this study 12 pairs of boots were worn (2 pairs by each of 6 participants) while 

engaging in common activity. Variables contributing to the formation of marks such as 

the style and condition of the boots, the walking path, environmental conditions, and 

duration of use were controlled. Following this activity each of the outsoles had 

acquired sufficient characteristics to be identified supporting the hypothesis that 

damage to outsoles is randomly acquired and provides for the possibility of 

individualization.

Bessman, C.W., Schmeiser, A. Survey of Tire Tread Design and Tire Size as Mounted on 

Vehicles in Central Iowa, Journal of Forensic Identification, 51(6), 2001, 587-596

The authors surveyed the tires of 1250 vehicles and determined that most (slightly more 

than 70%) of the vehicles had four tires with matching tread designs. The next most 

likely combination is two pairs of matching tires. A small percentage of vehicles were 

found to have tires of four different tread designs.

Birkett, J. Variations in Adidas “Kick” and Related Soles, MPFSL Report Number 34, 

Metropolitan Police Forensic Science Laboratory, London, 1983

Impressions from 78 sole units of the same type were evaluated and compared. The 

soles were produced by cutting from calendared rubber material. It was determined 

that 77 of the soles were clearly distinguishable based on manufacturing characteristics. 

The remaining pair was also distinguishable, however, the distinguishing features were 

more subtle and may not be clear in casework type impressions were smudging is 

present. 

Bodziak, William J., Footwear Impression Evidence: Detection, Recovery, and 

Examination, 2nd edition, Chapter 10, Class and Identifying Characteristics, pp. 329-

356, CRC Press, Boca Raton, Florida, 2000

The author discusses both class and identifying characteristics and gives theoretical and 

actual examples of their use and significance.
Bodziak, William J., Manufacturing Processes for Athletic Shoe Outsoles and Their 

Significance in the Examination of Footwear Impression Evidence, Journal of Forensic 

Sciences, 31(1), 153-176

This article explains how each of the most common manufacturing process creates 

features that may be useful in the examination of impressions. The article presents the 

specific type of class and or individual characteristics created as part of each 

manufacturing process, the relative uniqueness of these characteristics, and their 

significance in drawing conclusions regarding impressions made by the shoes.

Bodziak, William J., Tire Tread and Tire Track Evidence: Recovery and Forensic 

Examination, Chapter 9, Individual Characteristics, pp. 209-221, CRC Press, Boca 

Raton, Florida, 2008

Cassidy, Michael J., Footwear Identification, Government of Canada Press, 1987

The author conducted research involving the examination of wear and individual 

characteristics produced in 194 impressions from the heels of boots worn in the same 

geographic area. With regard to individual characteristics, the author concluded that 

size of the individual characteristic is not the most important factor in examination and 

each individual characteristic must be evaluated on its own merit taking into account 

the shape and the quality of recording of the impression.

Champod, C., Voisard, R., Girod, A., A statistical study of air bubbles on athletic 

shoesoles, Forensic Science International, 109, 105-123

An area on the outsole of 71 pairs of shoes (142 shoes) of common outsole pattern, size, 

and manufacturer was evaluated with the goal of assessing the statistical variability and 

independence of air bubbles created during the manufacturing by the injecting molding 

process. The authors found air bubble configurations in this sample set were highly 

variable in this sample set; however, the adoption of a simple statistical model to 

predict the probability of a given configuration was not possible. Further, the authors 

found that the data generated in this study could only be applied to assess the 

specificity of air bubble configurations on shoes from this particular production line. In 

short, the variables involved in the production of air bubbles following the injection 

process make every situation very specific in terms of the probability of the random 

occurrence of a given configuration even if the variables of general pattern, 

manufacturer, and size are controlled. 

Davis, R.J and Keeley, A. Feathering of Footwear, Science and Justice, 40(4), 2000, 273-

276.

Feathering was produced on outsole test samples in the laboratory and the no 

significant matches were found between the samples, even those taken from the same 

area of different outsoles produced in the same mold. No matches were found between 

training shoes produced in the same mold and worn for the same length of time by the 

same person.
Hamburg, C. and Banks, R. Evaluation of the Random Nature of Acquired Marks on 

Footwear Outsoles, unpublished, presented at the 2010 Impression and Pattern 

Evidence Symposium, Clearwater Beach, Florida, August 2010.

This project evaluated the marks acquired on four pairs of shoes (two subjects each 

wearing two pairs of shoes). Variables including outsole design, wearer, travel paths, 

and length of wear were controlled. All right shoes and all left shoes were compared to 

each other. No acquired marks were found to repeat.

Hamm, E.D. The Individuality of Class Characteristics in Converse All-Star Footwear, 

Journal of Forensic Identification, 39(5), 1989, 277-292

The author discusses the manufacturing process for Converse All-Star shoes and 

demonstrates how each step of the process has the potential to impart certain features. 

When the combination of features is considered, the population of shoes that share the 

same combination of characteristics can be significantly narrowed even when the shoes 

are of the same general design and size.

Hanningan, T.J., Fleury, L.M., Reilly, R.B., O’Mullane, B.A., deChazal, P. Survey of 1276 

sheoprint impressions and development of an automatic shoeprint pattern matching 

facility, Science and Justice, 46(2), 2006, 79-89

1276 outsole pattern impressions were obtained from male attendees at a scientific 

exhibition. The patterns were sorted and it was determined that the largest group of 

outsoles sharing a common overall design represented only 1% of the sample set. Each 

of the other outsole designs represented a significantly smaller proportion of the 

sample set. 773 outsole designs occurred only one time. The authors conclude that 

even a correlation in outsole design can be potentially significant evidence.

Kainuma, A. Manufacturing Variations in a Die-Cut Footwear Model, Journal of 

Forensic Identification, 55(4), 2005, 503-517

100 pairs of shoes produced using the die-cut manufacturing process were evaluated for 

variations imparted during the manufacturing process. No two pairs shared identical 

class features.

Jay, C.B. and Grub, M.J. Defects in Polyurethane-soled Athletic Shoes – Their 

Importance to the Shoeprint Examiner, Journal of the Forensic Science Society, 25: 

233-238

The authors examine the occurrence of bubbles in polyurethane soles and conclude that 

within a given shoe sole design there will be some similarity in pattern of bubbles.

Keijzer, J. Identification Value of Imperfections in Shoe with Polyurethane Soles in 

Comparative Shoeprint Examination, Journal of Forensic Identification, 40(4), 1990, 

217-223

Twenty-two shoe soles (fourteen left and eight right) of the same make and model were 

evaluated for similar imperfections. Air bubbles were often found to occur in the same 

places on the sole surfaces and were sometimes similar in shape and size. Factors 
affecting the location, size, and shaped appeared to be the form of the sole surface and 

the high degree of accuracy of the manufacturing process.

Music, D.K., Bodziak, W.J., Evaluation of the air bubbles present in polyurethane shoe 

outsoles as applicable in footwear impression comparisons, Journal of Forensic 

Sciences, 33(5), 1988, 1185-1197

The chemical, physical, and mechanical factors influencing the formation of air bubbles 

in polyurethane shoe outsoles are discussed with regard to the various manufacturing 

techniques. The authors present factors for consideration in interpreting the relative 

uniqueness of air bubbles encountered in casework. 

Parent, S. The Significance of Class Associations of Footwear Evidence, unpublished, 

poster presented at the 2010 Impression and Pattern Evidence Symposium, 

Clearwater Beach, Florida, August 2010.

1607 shoeprints (1,290,421 possible pairs) were collected from the general public in 

various cities in the state of Texas. The shoeprints were compared with regard to tread 

design, size, and general wear condition and no two shoeprints were found to be the 

same. Shoeprint comparisons involving both the two and heel of the shoe proved to be 

more discriminating than partial prints involving only the toe. 

Petraco, N.D., Gambino, C., Thomas, K.A., Oivio, D., Petraco, N. Statistical 

Discrimination of Footwear: A Method for the Comparison of Accidentals on Shoe 

Outsoles Inspired by Facial Recognition Techniques. Journal of Forensic Sciences 2010; 

55(1)In this study a statistical technique used in facial pattern recognition (maximum 

likelihood Gaussian linear classification) was applied to evaluate acquired marks on five 

pairs of shoes worn by the same individual for a period of thirty days. In order to 

maximize potential similarity, only the location of the marks was evaluated. Factors such 

as size, shape, and orientation were not considered and only a portion of the sole was 

evaluated. Despite the fact that only a small amount of the information typically 

available to an impressions examiner was utilized, this method was usually able to 

identify which shoe generated a particular pattern. According to the authors, “The high 

correct classification rates from our minimally detailed data lend a great deal of 

credence to the proposition postulated by imprint examiners of the “uniqueness” of 

accidental patterns. If data are also recorded for the physical characteristics of each 

accidental, the above results indicate that this method would be even more successful 

in identifying a shoe from one or more related accidental patterns.”

Stone, R.S., Footwear Examinations: Mathematical Probabilities of Theoretical 

Individual Characteristics, Journal of Forensic Identification, 56(4), 2006, 577-599

Theoretical types of individual characteristics are discussed and a statistical model for 

the evaluation of the probability of occurrence of each type of mark and of 

combinations of marks is presented.
Tart, M.S., Downey, A.J, Goodyear, J.G., Adams, J. The Appearance of Feathering as a 

Feature of Wear, The Forensic Science Service, (FSS Report No. RR 786) 1-11

Twenty-seven pairs of shoes were assessed to determine the frequency and earliest 

time of occurrence of feathering, the stability of the pattern, and the similarity of 

pattern between outsoles. The authors conclude that feathering occurs commonly with 

minimal wear, the patterns commonly change over relatively short periods of time, and 

the patterns can be distinguished between soles with similar states of wear. The findings 

indicate that feathering patterns can be used as highly distinguishing characteristics. 

Zmuda, C.W. Identification of Crepe-Sole Shoes, Journal of Criminology, Criminal Law 

and Police Science, 44 (3): 374-378 

Nearly 200 crepe soles shoes, over 100 consecutively cut soles and nearly 50 sole 

assemblies were examined. No two soles were found to be exactly alike.

QUESTION 13

What is the literature on quantification; measurement precision and uncertainty in 

shoeprint/tire tread examinations? For example, are there studies that would help 

describe “small” and “large” scratches in terms of measurement uncertainty? For 

example, is > 1.0 cm plus/minus 0.1cm big and how jagged does a scratch need to be 

before it is unique?

Individual characteristics have a location and orientation on the known item, and may 

range from minute to various measurements. However, when the item impresses on a 

surface, the measurement of a cut, scratch or gouge can be different based on a 

number of variables including the type, flexibility or degree of hardness of the surface 

they are impressed upon or the amount of weight or pressure placed on the item 

when it made the impression. Precise measurement of the characteristic is therefore

not as significant as the clarity of the feature, its specific location and orientation on 

the item, and whether it corresponds to the impression left behind.

Stone, Rocky S. Footwear Examinations: Mathematical Probabilities of Theoretical 

Individual Characteristics. Journal of Forensic Identification 56, 4 ( Jul/ Aug 2006) 577-

599.

The author quantifies individual characteristics that appear on a shoe impression using 

two primary variables: their location and their configuration . Theoretical types of 

individual characteristics that are found on shoe prints are described and a hypothetical 

model is presented with probability estimates applied to quantify the likelihood of 

occurrence of the characteristics. 

The author also discusses combinations of characteristics where more than one 

individual characteristic exists, and the application of this research to partial footwear 

impressions and tire impressions. 
Adair, T. W., Lemay, J., McDonald, A.,Shaw, R., Tewes,R. The Mount Bierstadt Study: 

An Experiment in Unique Damage Formation in Footwear. Journal of Forensic 

Identification 57,2 ( Mar/Apr 2007) 199-205

The authors obtained new boots, made test impressions of them, then wore the boots 

over the same path at the same time on a hike, with each person wearing two pairs of 

boots during the experiment. The of the 38 elements of the boots were given specific 

address locations and individual characteristics in each location were recorded.

Comparisons conducted between all of the outsoles at each of these address locations, 

found that there were no corresponding marks at any locations, supporting the 

reliability of partial impression comparisons. 

Bodziak, W.J. Footwear Impression Evidence Detection , Recovery and Examination 

2nd Edition, CRC Press, 2000

The author describes individual characteristics, and the random nature of the size,

shape, orientation and/or position, and indicates that they can range from the tiniest, 

almost obscure pinpoint sized characteristic to one having tremendous distinctness.

Considerations must include clarity, reproducibility and repeatability and confirmation 

of random occurrence, as well as degree of uniqueness based on size, shape, position 

and orientation. Clarity plays an important role, and the association of the 

characteristic between the known item and the questioned impression must be 

demonstrable. 

He also discusses the value of one confirmable random characteristic based simply on 

the random placement/location on the item and the concept that one single 

characteristic can have multiple features within it. 

Cassidy, Michael J., Footwear Identification Government of Canada Press, 1987

The author conducted a research project involving 194 heel impressions of boots worn 

in the same geographical area ( RCMP Training Academy) examining wear and 

accidental (individual) characteristics to determine the possibility of accidental 

characteristics reoccurring in the same place on other shoes, and the incidence of 

general wear being repeated.

Approximately 10,000 examinations were conducted. The author concluded that each 

characteristic must be weighed on its own individual merits and that how the 

characteristic is individually shaped and how accurately they are recorded is more 

important than the size of the characteristic.

QUESTION 14

What is the literature on population-based studies that describe variation (e.g. due to 

gender, pathologies, height/weight, running vs. walking, stride, etc)?

Barton, C. J., Bonanno, D., & Menz, H. B. (2009). Development and evaluation of a tool 

for the assessment of footwear characteristics. Journal of Foot and Ankle Research, 

2:10.
This article discusses footwear characteristics that have been linked to falls in older 

adults and children and how they may have an effect on the development of many 

musculoskeletal conditions due to the relationship between footwear and 

pathology. The goal was to develop a simple, efficient, and reliable footwear assessment 

tool potentially suitable for use in a range of patient populations that would allow for an 

accurate and efficient critique on an individual's footwear. The study resulted in the 

development of a comprehensive footwear assessment tool to assist with future 

research and clinical footwear assessment. The tool has good reliability and can be used 

with confidence in research and clinical settings, but further research is needed to 

determine the clinical validity of each item in various patient populations.

Whittle, M. W. (1996). Gait analysis: An introduction, Second edition. Oxford, England: 

Butterworth-Heinemann.

Ostrosky, K. M., VanSwearingen, J. M., Burdett, R. G. & Gee, Z. A comparison of gait 

characteristics in young and old subjects. (1994). Physical Therapy, 74(7), 637-644.

The purpose of this study was to describe and compare active range of motion during 

free-speed gait in younger and older people. Sixty volunteers in good health were 

studied. Thirty subjects (15 male, 15 female) were between 20 and 40 years of age, and 

30 subjects (15 male, 15 female) were between 60 and 80 years of age. Methods. 

Subjects were videotaped walking down a 6-m walkway with reflective markers at six 

locations along their right side. The videotape was analyzed for nine gait characteristics 

using a two-dimensional video motion analysis system. Differences in gait characteristics 

between the two groups were examined using a multivariate analysis of variance, 

followed by univariate F tests. Results. Two gait variables—knee extension and stride 

length—were significantly different between groups, and differences in velocity 

approached significance. For individuals in good health, the gait of older people differs 

from the walking pattern of young people for selected variables. Older people 

demonstrate less knee extension and a shorter stride length compared with younger 

people. Differences in self-paced walking velocity between old and young people may 

have influenced the gait characteristics measured.

Cassidy, M. J. (1980). Footwear identification. Identification of footwear evidence (pp. 

98-108). Quebec, Canada: Canadian Government Printing Centre.

Murray, M.P., Kory, C., Clarkson, B. H., & Sepic, S. B. (1966). Comparison of the free 

and fast speed walking patterns of normal men. American Journal of Physical 

Medicine & Rehabilitation, 45 (1), 8-24.

Murray, M. P., Drought, A. B., & Kory, R. C. (1964). Walking patterns of normal men. 

The Journal of Bone and Joint Surgery, 46 (2), 335-360.

A simple and inexpensive photographic method has been developed whereby many 

kinematic components of the walking act in the sagittal, frontal, and transverse planes 

can be measured and related temporally. A factorial design was used to study the 
displacement patterns of sixty normal men who ranged in age from twenty to sixty-five 

years and in height from sixty-one to seventy-four inches. Each subject's weight was 

within normal limits for his height and frame size. There was striking similarity in the 

duration of successive phases of stance, swing, and double-limb support during the 

same walking trial and during repeated trials of the same subject. Step and stride length 

and stride width showed the same striking similarity. Foot angles, however, showed 

greater individual variability. The differences in timing and stride dimensions did not 

relate systematically with age. However, the subjects sixty to sixty-five years old differed 

from younger subjects in that they took shorter steps and strides and showed a greater 

degree of out-toeing. The only variables which related systematically with height were 

the step and stride lengths, with the tall subjects taking the longest steps and strides 

and the short subjects, the shortest. Seven displacement patterns of free-cadence 

walking were analyzed for sixty normal men from twenty to sixty-five years old and from 

sixty-one to seventy-four inches tall. These displacement patterns include sagittal 

rotation of the pelvis, hip, knee, and ankle and vertical, lateral, and forward movement 

of the trunk. Each movement pattern was strikingly similar for repeated trials of the 

same subject and for subjects in the various age and height groups. Slight differences in 

the magnitude of hip flexion excursion occurred, which showed a low positive 

correlation with age and a similarly low but negative correlation with height. There was 

no evidence of presenile changes in these excursions among our oldest subjects, except 

for some decrease in the magnitude of ankle extension at the end of the stance phase. 

The serial transverse rotations of the pelvis and thorax have been analyzed in freecadence walking of sixty normal men. Although there was striking similarity in these 

excursions for repeated trials of the same subject, there was wide variation in these 

excursions among the subjects in similar age and height categories. These variations 

suggest that pelvic and thoracic rotation are not obligatory elements of normal gait. The 

decreased pelvic rotation in the group sixty to sixty-five years old may possibly 

represent another aspect of the presenile pattern of walking.

Drillis, R. J. (1958). Objective recording and biomechanics of pathological gait. Annals 

of the New York Academy of Sciences, 74, 86-109.