Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

1 of 16

Document #10

Standards for Examining Friction Ridge 

Impressions and Resulting Conclusions

(Latent/Tenprint)

1. Preamble

1.1. Friction ridge impression examinations are conducted by examiners using the Analysis, Comparison, 

Evaluation, and Verification (ACE-V) methodology, which include both qualitative and quantitative 

aspects. ACE is not generally applied as a strictly linear process because it may include a return to any 

previous phase. Application of ACE includes observations, measurements, assessments, decisionmaking, and documentation, which are enabled by the education, training, skill, and experience of the 

examiner.

1.2. The examination of friction ridge impressions and the resulting conclusions are based on ridge flow and 

ridge paths; the location, direction, and spatial relationships of minutiae; and ridge structure. The 

analysis phase leads to the determination of suitability. Following comparison, the evaluation phase 

leads to the following conclusions: individualization, exclusion, or inconclusive. These conclusions are 

based on the following premises [1] [2]:

1.2.1. Friction ridge skin bears an extremely complex, unique, and persistent morphological structure.

1.2.2. Notwithstanding the pliability of friction ridge skin, the contingencies of touching a surface, and 

the nature of the matrix, an impression of friction ridge skin structure may be left following 

contact with a surface.

1.2.3. This impression may display features of varying quality (clarity of ridge features) and specificity 

(weighted values and rarity).

1.2.4. Notwithstanding variations in clarity and specificity, the unique aspects of friction ridge skin 

may be represented as highly discriminative features in impressions.

1.2.5. An impression that contains sufficient quality and quantity of friction ridge features can be 

individualized to, or excluded from, a source.

1.2.6. The use of a fixed number of friction ridge features as a threshold for the establishment of an 

individualization is not scientifically supported.

2. Scope

2.1. The ACE-V methodology of friction ridge impression examination utilizes a qualitative and quantitative 

assessment of Level 1, Level 2, and Level 3 details.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

2 of 16

2.2. The ACE-V methodology is applied to examinations and comparisons of friction ridge impressions. This 

document illustrates the case of unknown to known comparisons but is applicable to other comparisons 

(e.g., known to known).

2.3. The application of the ACE-V methodology to casework requires examiner competency as established 

through training and testing [3].

3. Factors Affecting Examinations

3.1. The following factors affect the qualitative and quantitative aspects of friction ridge impressions. A 

competent examiner [3] will understand these factors, recognize that they occur in friction ridge 

impressions, and understand how they influence friction ridge impression reproducibility. These factors 

may cause an apparent dissimilarity between impressions from the same source. Failure to properly 

assess the occurrence and influence of these factors could result in misinterpretation. When applicable, 

the following factors must be considered in all steps of the ACE-V methodology:

3.1.1. Anatomical aspects include the condition of the skin (e.g., scars and warts) and the 

morphology of the hand and foot relative to the shape and contour of the substrate.

3.1.2. Transfer conditions include pressure applied during transfer, slippage or twisting, sequence of 

deposition (i.e., double taps and overlays), and an understanding of the limitations of friction 

ridge pliability.

3.1.3. Matrix includes bodily secretions and contaminants (e.g., sweat, blood, paint, dirt, oil, grease).

3.1.4. Detection techniques that can be one or more of the following: optical (i.e., light sources and 

illumination techniques), physical, or chemical processing techniques.

3.1.5. Recording or preservation techniques, such as photography, lifting, live-scan, and ink.

3.1.6. Substrate (e.g., porous, non-porous, semi-porous, smooth, rough, corrugated, pliable, or 

textured surfaces).

3.1.7. Environmental conditions (e.g., protected, unprotected, wet, dry, cold, or hot).

4. Levels of Friction Ridge Impression Detail For Examinations

Level 1 detail refers to the overall ridge flow. Level 2 detail refers to individual friction ridge paths, friction ridge 

events (e.g., bifurcations, ending ridges, dots, and continuous ridges), and their relative arrangements. Level 

3 detail refers to ridge structures (edge shapes and pores), and their relative arrangements. Creases, scars, 

warts, incipient ridges, and other features may be reflected in all three levels of details1.

5. Procedure for Friction Ridge Impression Examinations (ACE-V Methodology)

5.1. Analysis

5.1.1. Analysis includes the assessment of the impression to determine its value based on Level 1, 2, 

and 3 detail. This assessment is affected by other relevant information as described in section 

2, as well as possible anatomical origin and orientation. Analysis determines if the impression 

is suitable for comparison. If the impression is not suitable, the examination will stop at the

analysis phase and will be reported as such2. If the impression is suitable, the analysis further 

indicates the features and their tolerances to be used in the comparison.

5.1.2. In the analysis phase, the examiner assesses the friction ridge skin features and determines 

the tolerances assigned to the impressions (unknown and known). Tolerance is the allowance 

of variation in appearance of friction ridge features (due to the factors listed in section 3) that 

will be accepted during comparison, should the corresponding print be available.

 1

 For example, a crease could exhibit Level 1 crease flow, Level 2 crease path, and Level 3 crease shape.

2

 It will not be reported as inconclusive, but may be submitted to verification.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

3 of 16

5.1.3. The analysis may also provide anatomical information to prioritize the potential corresponding 

areas and limit unnecessary comparisons. Certain orientation indicators such as recurves, 

deltas, creases, and scars may provide specific guidance where to begin the comparison.

5.1.4. Determination of suitability

5.1.4.1. The determination of suitability is based on the assessment of the discriminating 

strengths of the features and their arrangements. Suitability is the determination that 

there is adequate quality and quantity of friction ridge features in an impression for 

some further process step. The assessment is made based on the quality of 

features (clarity of the observed features), the quantity of features (amount of 

features and area), the specificity of features, and their relationships (see section 5).

5.1.4.2. There are commonly two approaches to the determination of suitability often 

adopted as agency policy:

5.1.4.2.1. Approach #1 (commonly referred to as “of value for identification”): Only 

impressions of value for individualization are compared. Value for 

individualization indicates an impression that is deemed to be 

identifiable. When adopting this approach, impressions lacking value for 

individualization are not further compared.

5.1.4.2.2. Approach #2 (commonly referred to as “of value for comparison”): 

Impressions of value for individualization and impressions only of value 

for exclusion are compared. 

5.1.4.2.3. Conclusions in the evaluation phase following both approaches are: 

individualization, exclusion, or inconclusive.

5.2. Comparison

5.2.1. If the analysis phase provides indicators as to the probable anatomical area, a side-by-side 

comparison with the appropriate area of the known print is initially conducted. In the absence of 

indicators, all areas of available known impressions must be compared. 

5.2.2. Comparison is accomplished through the side-by-side observation of all levels of details to 

determine whether the two impressions are in agreement or disagreement based upon 

features, sequences, and spatial relationships within the tolerances of clarity and distortion.

5.2.3. Comparison begins with the determination of dissimilarity or similarity between two impressions 

at Level 1. If similarity is determined within tolerance at Level 1, a target group is selected from 

the features observed during the analysis phase and is then searched within the selected area 

of the other impression. When similarity with the target group exists, additional contiguous 

arrangements of features are compared between impressions in a cyclical or recurring process 

from the unknown to the known impression to evaluate disagreement or agreement between 

the impressions. The process can be extended to comparing features in the known with 

features in the unknown that were reanalyzed during the comparison phase. If the initial target 

group is not found, alternative target groups may be selected and compared.

5.2.4. Observation of agreement or disagreement between the impressions initiates the evaluation 

phase.

5.3. Evaluation

5.3.1. Once the examination progresses from the comparison phase into the evaluation phase, it is 

determined whether the information is sufficient (see section 6) to form one of the three 

conclusions or return to the analysis phase and reassess suitability3.

 3

 This would not be necessary under approach 2.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

4 of 16

5.3.2. In the evaluation phase, the examiner will ultimately decide whether the unknown impression is 

from a different source or the same source as the compared impression, or is inconclusive. 

These conclusions are defined below.

5.3.2.1. Exclusion

Exclusion is the decision by an examiner that there are sufficient features in 

disagreement to conclude that two areas of friction ridge impressions did not 

originate from the same source. Source refers to the area of friction skin. Exclusion 

of a subject can only be reached if all relevant comparable anatomical areas are 

represented and legible in the known exemplars. Notes and reports shall clearly 

state if the exclusion refers only to the source or the subject.

5.3.2.2. Individualization

Individualization is the decision by an examiner that there are sufficient features in 

agreement to conclude that two areas of friction ridge impressions originated from 

the same source. Individualization of an impression to one source is the decision 

that the likelihood the impression was made by another (different) source is so 

remote that it is considered as a practical impossibility.

5.3.2.3. Inconclusive

5.3.2.3.1. An inconclusive conclusion resulting from a suitability decision as 

described in approach #1 in section 5.1.4.2.1 occurs when an examiner 

is unable to individualize or exclude due to an absence of complete and 

legible known prints (e.g., poor quality fingerprints and lack of 

comparable areas). In such an instance, the inconclusive conclusion 

means that the impression needs to be reexamined using clearly and 

completely recorded known impressions.

5.3.2.3.2. An inconclusive conclusion resulting from a suitability decision as 

described in approach #2 in section 5.1.4.2.1 can occur either as in 

approach #1 or when corresponding features are observed but not 

sufficient to individualize. Likewise dissimilar features may be observed 

but not sufficient to exclude. In either case, the inconclusive conclusion 

means that the unknown impression was neither individualized nor 

excluded as originating from the same source.

5.3.2.3.3. There may be other instances where agencies have adopted 

procedures to report inconclusive conclusions. These are left to the 

administrative policies and procedures of the individual agency. 

However, these policies and reporting procedures must be clearly 

defined by the agency.

5.3.3. Reporting Conclusions

The conclusions of individualization and exclusion will be documented in notes and in reports; 

however, the determining factors need not be included in reports. Reasons for reaching 

inconclusive conclusions must be documented in notes and included in reports.

5.4. Verification

5.4.1. The independent application of the ACE process is utilized by a subsequent examiner to either 

support or refute the conclusions of the original examiner.

5.4.2. Suitability determinations may be verified by another examiner trained to competency [3]. A 

conclusion of individualization shall be verified. All other conclusions resulting from the 

evaluation phase should be verified.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

5 of 16

5.4.3. Conflict resolution shall take place if the original conclusion is contested and cannot be 

resolved through consultation [5].

5.5. The flowchart in Appendix A details the major steps of ACE-V. The chart has been adapted from the 

NIST (National Institute of Standards and Technology) Expert Working Group on Human Factors in 

Latent Print Analysis. It is offered here as supporting documentation and applies to both tenprint and 

latent print examination.

6. Sufficiency for Conclusions

6.1. Sufficiency is a product of the quality and quantity of the objective data under observation (e.g., friction 

ridge, crease, and scar features). As the quality of an impression increases the need for quantity of 

friction ridge features decreases, as well as the inverse.

6.2. Quality

6.2.1. Quality is the assessment of the clarity of ridge features. Generally as quality increases so 

does the discernability and reliability4 of the ridge features. It is recognized that quality is not 

necessarily constant throughout an impression. The assessment of quality may represent just 

the areas of highest quality, a range of qualities, or a map or rating system of quality of various 

regions in a single impression.

6.2.2. Table 1 shall be used for categorizing the levels of quality of the features in an impression 

(unknown or known). The level of quality determines the degree of tolerances that will be used 

during the comparison process. High quality will lead to low tolerances and conversely low 

quality will require high tolerances5.

Quality

High

Level 1 is distinct;

Level 2 details are distinct;

There are abundant distinct Level 3 details.

Medium High 

Level 1 is distinct;

Most of the Level 2 details are distinct;

There are minimal distinct Level 3 details.

Medium Low

Level 1 is distinct;

Few of the Level 2 details are distinct;

There are minimal distinct Level 3 details.

Low

Level 1 may not be distinct;

Most of the Level 2 details are indistinct;

There are no distinct Level 3 details.

Table 1: Categories of quality defined as a function of levels of details observed.

 4

 Reliability refers to the confidence assigned by the examiner to the observed ridge features in terms of 

existence, location, and shape he or she would expect to be reproduced on the corresponding print, should it be 

made available.

5

 High tolerances: generous allowances for variations in appearance and spatial relationships.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

6 of 16

6.2.3. The above quality metric was designed to allow for a range of quality assessment as opposed 

to a narrow categorization. Table 1 provides four ranked categories for the quality metric. 

There are subjective as well as objective elements to this categorization, but the descriptions 

provided in the table should allow a meaningful quality description to be made with reference to 

the categories.

6.3. Quantity

6.3.1. Quantity, as applied in this section, is the number of ridge endings, bifurcations, and dots 

(minutiae) in contiguous ridges, determined without any reference to known impressions. All 

minutiae are considered here including indistinct minutiae for which type or exact location 

cannot be established6. Overall quantity of all features in the impression is not part of this 

measure. 

6.3.2. It is recognized that this is an incomplete measure of the overall quantity of detail in a print. 

Level 2 detail encompasses more than minutia counts (including the ridge path, areas with 

open fields, and selectivity of minutiae). Minutia counts remain, however, as a discrete, 

measurable aspect of all prints and their enumeration is part of the systematic, formal 

consideration of quantity.

6.3.3. The utility of the number of minutiae as applied in this section is to assist in the analysis of 

suitability and the recognition of alternative levels of case complexity as they relate to 

sufficiency, evaluation, and verification. This use of the number of minutiae should not be 

considered as suggesting or endorsing the use of minutia counts as the sole criteria for a 

decision threshold.

6.4. Decision-Making

6.4.1. Sufficiency graph

6.4.1.1. The sufficiency graph (Figure 1) reflects the interplay between quality (defined in 

Table 1) and quantity of minutiae (as discussed in section 6.3) and its relation to the 

decision thresholds and levels of complexity based on a consensus of collective 

experience. It broadly represents how the amount of available information in an 

impression directly impacts the decision-making process. The sufficiency graph was 

developed to illustrate the intellectual process involved with the examination of 

friction ridge detail and the ensuing decisions. It represents the examiner’s 

understanding of the aggregate relationship of details. Its purpose is to illustrate a 

part of the process dealing with the analysis of the impression for sufficient quality 

and quantity of detail to proceed with the comparison effort. It also illustrates certain 

thresholds wherein examiners should recognize the need for, and provide, 

enhanced documentation supporting their conclusions.

6.4.1.2. The axes used to plot the decision of the examiner, the positions of the curves, and 

the underlying regions, were created based on a consensus of experienced 

examiners (SWGFAST). Considerations in establishing the graph are related to 

actual casework and include international practices, general awareness of 

longstanding, as well as current literature and trends in ongoing research.

6.4.1.3. Level 2 detail in this graph is represented on the horizontal axis by numbers of 

minutiae. The limitations and rationale for using this metric for quantity are 

discussed in section 6.3. It is re-emphasized here that this should not be considered 

as suggesting or endorsing the use of minutiae counts as the sole criteria for a 

decision threshold.

 6

 For example when a single ridge flows into a visually obscured area and two ridges emerge from the same area.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

7 of 16

6.4.1.4. The four categories of quality represented on the vertical axis are given in Table 1 

and discussed in section 6.2.

6.4.1.5. In Figure 1, the solid curve in the graph defines the lower limit of the sufficiency of 

friction ridge details below which, in area marked A, an individualization decision is 

not warranted. The dotted curve indicates the boundary between levels of 

complexity (complex versus non-complex). In area marked B in Figure 1, the 

examination is considered as complex and an individualization may be warranted. In 

area marked C in Figure 1, the examination is considered as non-complex and an 

individualization is warranted.

6.4.1.6. Quantity is meaningless in the absence of quality. Individualization cannot be 

achieved on quantitative considerations alone. It is recognized that in the absence of 

any minutiae, an individualization may be possible in such complex cases if the 

impression displays very high quality.

Figure 1: Sufficiency Graph

This graph does not suggest or endorse the use of minutiae counts as the sole criteria for a decision threshold.

6.4.2. Analysis phase

6.4.2.1. In the analysis phase, the assessment of the impression based on quality and 

quantity (as defined above) is positioned on the graph to determine its suitability for 

individualization. If the impression falls below the solid curve, then an 

individualization is not warranted. If positioned above the curve, then it may allow an 

individualization.

6.4.2.2. Minimum quality assurance measures are associated with each level of complexity 

according to the following table (Table 2):
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

8 of 16

Documentation [4] and verification procedures [5]

Non-complex

Limited documentation of the relevant features used as a basis 

for a conclusion.

Standard verification.

Complex

Extensive documentation of the relevant features used as a basis 

for a conclusion.

Should consider the possibility of an enhanced verification and 

review procedure (e.g., a blind verification and multiple verifiers).

Table 2: Documentation and verification procedures.

6.4.2.3. A non-complex impression may be classified as complex if the following modifying 

factors are present: low specificity of features, significant distortion (e.g., multiple 

tap, superimposed impression, extreme pressure leading to tonal reversal, and 

slippage), high tolerances, or the original conclusion is contested during verification. 

6.4.2.4. An impression categorized initially as complex may be classified as non-complex if 

modifying factors are present such as high specificity of features, presence of 

creases, scars, and open fields.

6.4.2.5. Justification for reassignment of complexity shall be documented.

6.4.3. Evaluation phase

6.4.3.1. In the evaluation phase, the sufficiency graph is used as a guide that broadly 

delineates the boundaries between individualization and inconclusive decisions.

6.4.3.2. In the evaluation phase, the decision process starts with an attempt at exclusion 

followed by an assessment of the potential correspondence observed between the 

impressions.

6.4.3.2.1. Exclusion (See Appendix B)

6.4.3.2.1.1. An exclusion decision can be based solely on Level 1 

when sufficient pattern area and orientation indicators 

(e.g., recurves, cores, deltas, and creases) are available 

and when disagreement has been observed absent any 

significant distortion such as: double tap, overlaid 

impressions, or twisting. If significant distortion is 

observed, an exclusion decision can only be reached by 

considering both Level 1 and Level 2 details. If available, 

Level 3 detail may also be considered in conjunction with 

Level 2 detail.

6.4.3.2.1.2. An exclusion decision can be based on Level 2 detail 

when sufficient disagreement has been observed.

6.4.3.2.1.3. Level 3 details cannot be the sole factor in exclusion 

decisions. Level 3 details have to be considered in 

conjunction with Level 1 and Level 2 details.

6.4.3.2.2. Individualization

6.4.3.2.2.1. If the impressions originated from the same source, the 

examiner should observe correspondence, within 
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

9 of 16

tolerances, of all features. It is the degree of 

correspondence of features that is weighed.

6.4.3.2.2.2. For an individualization conclusion, sufficient agreement 

of information must exist so that the likelihood the 

impression was made by a different source is so remote 

that it is considered as a practical impossibility.

6.4.3.2.2.3. Level 3 details cannot be the sole factor in 

individualization decisions. Level 3 details have to be 

considered in conjunction with Level 1 and Level 2 

details.

6.4.3.2.3. If the examiner did not reach a conclusion of individualization or 

exclusion, the conclusion will be reported as inconclusive.

7. References

[1] IAI 2010-18 resolution.

[2] Polski, J.; Smith, R.; Garrett, R. The Report of the International Association for Identification, 

Standardization II Committee. Grant no. 2006-DN-BX-K249 awarded by the U.S. Department of Justice, 

Washington, DC, March 2011. 

[3] SWGFAST Document #18 (2010), Standards for Minimum Qualifications and Training to Competency for 

Friction Ridge Examiner Trainees (Latent/Tenprint), Ver. 2.0.

[4] SWGFAST Document #8 (2012), Standard for the Documentation of Analysis, Comparison, Evaluation, 

and Verification (ACE-V) (Latent), Ver. 2.0.

[5] SWGFAST Document #7 (2012), Standard for a Quality Assurance Program in Friction Ridge 

Examinations (Latent/Tenprint), Ver. 5.0.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

10 of 16

Appendix A
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

11 of 16

Appendix B

8. Exclusion of Source or Subject

8.1. Exclusion is the decision by an examiner that there are sufficient features in disagreement to conclude 

that two friction ridge impressions originated from different sources. Exclusion implies that the 

likelihood of observing these features in disagreement, if the impressions are coming from the same 

source, is so remote that it is considered as a practical impossibility. 

8.2. Excluding a known friction ridge impression as the source of an unknown impression requires that the 

examiner has determined that the anatomical region indicated in the unknown impression is fully 

represented in the exemplar. Exclusion of a subject as the origin of the unknown impression can only 

be reached if all relevant comparable anatomical areas are represented and legible in the known 

exemplars. Notes and reports shall clearly state if the exclusion refers only to the source or the subject. 

8.3. When the impressions are determined to be non-complex, as determined in the analysis phase, 

exclusion can be simple. For example when the fingerprint is an impression of an arch pattern and the 

specific known impression under consideration is a whorl pattern the exclusion of that source is 

warranted (Figure B1). 

Figure B1: High quality impressions with unambiguous features may be excluded 

as having a common source based on Level 1 detail.

8.4. The “One Discrepancy Rule” or the “One Dissimilarity Doctrine” as described by Thornton [Appendix B: 

1], has been used to support exclusions of a source to an unknown impression. Although sometimes 

used synonymously and applied inconsistently, the terms “discrepancy” and “dissimilarity” refer to 

different concepts. Discrepancy refers to the presence of one or more friction ridge details in one 

impression that do not exist in the corresponding area of another impression [Appendix B: 2]. 

Discrepancies originate in the source skin. The term discrepancy is only used as a description of 

incompatibility between two impressions that has resulted in a conclusion of exclusion. It has long been 

recognized by latent print examiners that this “rule” should be critically applied with a detailed analysis 

of the remainder of the impression. Dissimilarity refers to a difference in appearance between two 

friction ridge impressions. For example, in the presence of overwhelming correspondence of features 

supporting the conclusion of individualization, an isolated dissimilarity may not be sufficient to exclude. 

Such a dissimilarity may be accepted as an artifact of distortion in the print or scarring in the skin 

without the examiner knowing the actual cause of the dissimilarity. 
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

12 of 16

8.5. The “One Discrepancy Rule” has been historically associated with minutiae and was applied only in 

cases with pattern similarity. It was often applied when a numerical threshold (typically eight to twelve 

minutiae) was required before deciding source attribution. 

8.6. In assessing dissimilarities, the examiner must scrutinize the impression concentrating on ridge 

morphology and specifically considering factors such as distortion, multiple overlapping impressions, 

compression, and scarring (Figures B2 & B3). Skin creases, which may have diminished or become 

more prominent over time, could also account for the appearance of misaligned ridges. It is incumbent 

on the examiner to acknowledge the differences, when present, and fully document the data used in 

the decision-making process.

Figure B2: In this instance an exclusion decision has been made because few features 

supporting individualization and an un-reconciled dissimilarity has been observed and determined 

by the examiner to be a discrepancy.7

Figure B3: In this instance an individualization conclusion has been reached because the 

abundance of features supporting individualization outweighs the presence of dissimilarities even 

though some may be of indeterminate origin.8

 7 Illustrations are intended to represent concepts of decision-making and not a numerical standard on which to 

base those decisions.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

13 of 16

8.7. There are instances where, for example, due to accident, disease or intentional disfigurement, 

fingerprint patterns, or ridge flow may change and take on the appearance of a different pattern or ridge 

configuration. Examiners making exclusions based on Level 1 detail must be aware of these 

phenomena and account for their influence as part of the decision making process (Figure B4). 

Figure B4: The example above illustrates a situation where, due to an injury, the impression on the right has a 

substantially different Level 1 pattern appearance from the pre-injury impression on the left.

8.8. Extra ridges may appear in a friction ridge impression even though there is an abundance of 

corresponding features between two impressions. This may be caused by movement of the friction 

ridge skin or surface at the time of deposition. Examiners making exclusions based on Level 2 detail 

must be aware of this phenomenon and account for its influence as part of the decision making process 

(Figure B5). 

 8 Illustrations are intended to represent concepts of decision-making and not a numerical standard on which to 

base those decisions.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

14 of 16

Figure B5: In this example, extra ridges, attributed to slippage during recording, resulted in a double tap solely in 

that area, while the remaining friction ridge surface remained as a single touch.

8.9. When the impressions are complex, the decision requires more expertise, consideration, and 

documentation of factors such as distortion and multiple depositions. Friction ridge details are not 

always accurately replicated in low quality impressions and variations in appearance of ridge 

characteristics and their sequence may be present. It should be noted that variations may also appear 

in high quality prints. Caution is warranted in the determination of whether a variation is a dissimilarity 

rather than a discrepancy (Figures B6 and B7). 

Figure B6: In the example above there is the potential of an erroneous exclusion based on Level 1 pattern. The 

impression contains red flags that would be cause to question the reliability of Level 1. Level 2 details should be 

considered prior to the exclusion conclusion.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

15 of 16

Figure B7: In the real case example above, multiple examiners erroneously excluded the source due to apparent 

Level 1 ridge flow difference.

9. Conditions Supporting Exclusion

9.1. Expert consensus and experience have determined that source exclusion may be reliably made using 

Level 1 and Level 2 details. Exclusion relying predominantly on Level 3 detail is problematic due to 

inconsistency in its recording.

9.2. In order to reach a decision to exclude a source, the examiner must weigh the discriminating value of 

the features present in the impression that support individualization against those which support 

exclusion.

10. References

[1] "One-Dissimilarity Doctrine in Fingerprint Identification," J.I. Thornton, International Criminal Police 

Review, March 1977, Issue 306 Pages 89-95.

[2] SWGFAST Document #19 (2013), Standard Terminology of Friction Ridge Examination (Latent/Tenprint), 

Ver. 4.0.
Document #10 Standard for Examining Friction Ridge 

Impressions and Resulting Conclusions, Ver. 2.0

Date of First Issue 09/13/11 Current Issue Date 03/13/13

Web Posting Date 04/27/13

Date of Last Review N/A Date of Next Review 03-2018 Appendix present/Letter Yes/A&B

16 of 16

11. Revision Table

Version Effective Start Effective End Posted Archived Change

1.0 3/15/11 09/13/11 09/13/11 Original Issue

1.1 09/13/11 N/A 10/26/11 N/A 1. Revised numbering

2. Updated Appendix with final 

reference source version

2.0 03/13/13 N/A 04/27/13 N/A Added Appendix B

Reformatted (start of new 

version number)