OSAC 2022-S-0015 Standard Guide for 

Forensic Physical Fit Examination

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OSAC 2022-S-0015 

Standard Guide for 

Forensic Physical Fit 

Examination

Trace Materials Subcommittee

Chemistry: Trace Evidence Scientific Area Committee

Organization of Scientific Area Committees (OSAC) for Forensic Science
OSAC 2022-S-0015 Standard Guide for 

Forensic Physical Fit Examination

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OSAC Proposed Standard

OSAC 2022-S-0015 

Standard Guide for

Forensic Physical Fit Examination

Prepared by 

Trace Materials Subcommittee

Version: 2.0

September 2022

Disclaimer:

This OSAC Proposed Standard was written by the Trace Materials Subcommittee of the Organization of 

Scientific Area Committees (OSAC) for Forensic Science following a process that includes an open 

comment period. This Proposed Standard will be submitted to a standards developing organization and is 

subject to change.

There may be references in an OSAC Proposed Standard to other publications under development by 

OSAC. The information in the Proposed Standard, and underlying concepts and methodologies, may be 

used by the forensic-science community before the completion of such companion publications.

Any identification of commercial equipment, instruments, or materials in the Proposed Standard is not a 

recommendation or endorsement by the U.S. Government and does not imply that the equipment, 

instruments, or materials are necessarily the best available for the purpose.

To be placed on the OSAC Registry, certain types of standards first must be reviewed by a Scientific and 

Technical Review Panel (STRP). The STRP process is vital to OSAC’s mission of generating and 

recognizing scientifically sound standards for producing and interpreting forensic science results. The 

STRP shall provide critical and knowledgeable reviews of draft standards or of proposed revisions of 

standards previously published by standards developing organizations (SDOs) to ensure that the 

published methods that practitioners employ are scientifically valid, and the resulting claims are 

trustworthy.

The STRP panel will consist of an independent and diverse panel, including subject matter experts, 

human factors scientists, quality assurance personnel, and legal experts, which will be tasked with 

evaluating the proposed standard based on a comprehensive list of science-based criteria.

For more information about this important process, please visit our website 

at: https://www.nist.gov/topics/organization-scientific-area-committees-forensic-science/scientifictechnical-review-panels. 
OSAC 2022-S-0015 Standard Guide for 

Forensic Physical Fit Examination

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Standard Guide for Forensic Physical Fit Examination 

1. Scope

1.1 This guide covers the forensic physical fit examinations for the macroscopical and microscopical 

examinations of broken, torn, or separated materials for the purpose of determining whether or not they 

were once joined together to form a single object. This guide is intended as an overview of the process 

for the physical fit examination of these materials and to assist individuals in the evaluation and 

documentation of their physical comparisons.

1.2 This standard is intended for use by competent forensic science practitioners with the requisite formal 

education, discipline-specific training (see Practice E2917), and demonstrated proficiency to perform 

forensic casework.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included 

in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is 

the responsibility of the user of this standard to establish appropriate safety, health and environmental 

practices and determine the applicability of regulatory limitations prior to use. 

1.5 This international standard was developed in accordance with internationally recognized principles on 

standardization established in the Decision of Principles for the Development of International Standards 

issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. 

2. Referenced Documents 

2.1 ASTM Standards:

C1256 Practice for Interpreting Glass Fracture Surface Features

E1459 Guide for Physical Evidence Labeling and Related Documentation

E1492 Practice for Receiving, Documenting, Storing, and Retrieving Evidence in a Forensic Science 

Laboratory

E1610 Guide for Forensic Paint Analysis and Comparison

E1732 Terminology Relating to Forensic Science

E2225 Guide for Forensic Examination of Fabrics and Cordage

E2917 Practice for Forensic Science Practitioner Training, Continuing Education, and Professional 

Development Programs

E3260 Guide for Forensic Examination and Comparison of Pressure Sensitive Tapes

2.2 Other Documents:

ISO/IEC 17025 (2017) General Requirements for the Competence of Testing and Calibration Laboratories

OSAC Guide for Interpretation and Reporting in Forensic Comparisons of Trace Materials

3. Terminology

3.1 Definitions – For additional terms commonly employed for general forensic examinations see E1732 and 

for fractography see C1256.

3.2 Definitions of Terms Specific to This Standard:

3.2.1 arrest lines, n - a sharp line on the fracture surface defining the crack front shape of an arrested or 

momentarily-hesitated crack. (1)

3.2.2 fractography, n - the means and methods for characterizing fractured specimens or compounds. (1)

3.2.3 individual characteristics, n - the attribute(s) that establish(es) a single source. 

3.2.3.1 Discussion: other terms used include random accidental characteristics, randomly 

acquired characteristics, distinguishing characteristics.

3.2.4 physical fit, n - an association based upon the realignment of two or more items that demonstrate 

they were once joined together to form a single object.

3.2.4.1 Discussion - The term match (e.g., physical match, fracture match) is not recommended 

to be used as it can be misleading to the layperson.

3.2.5 scarp, n - subtle curved line on a fracture surface caused by interaction of a propagating crack and a 

liquid or a reactive environment. (1) 
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3.2.6 taphonomy - the study of the processes affecting remains after death (OSAC Lexicon).

3.2.7 technical review - a qualified second party’s evaluation of reports, notes, data, and other 

documentation to ensure there is appropriate and sufficient support for the actions, results, 

conclusions, opinions, and interpretations. (OSAC Preferred Term – Lexicon)

3.2.8 verification, n - provision of objective evidence that a given item fulfills specified requirements. 

ISO/IEC 17025 (2017) 

3.2.8.1 Discussion: the process through which the analyses of a forensic examiner are compared 

by a second, independent examiner so that the findings of the first examiner are corroborated, or can 

be corrected in situations where there is a disagreement.

3.2.9 Discussion: verifications can be open or blind. Blind verifications are more robust than 

open verifications.

4. Summary of Guide

4.1 Physical fit examination is the process of evaluating two or more items to form an opinion about whether 

they were once joined together. It is based on the premise that separation events (e.g., breaks, cuts, tears) 

are not reproducible, in whole or in part, because of the combination of applied forces, construction 

features, and material properties that can impart individual characteristics. 

4.2 Physical fit examinations can involve the assessment or reassembly of multiple pieces prior to the 

comparison of a questioned sample to a possible known source.

4.3 Separation occurs in a variety of ways (e.g., broken, cut, torn). Separated materials that possess irregular 

edges and individual characteristics on their complementary surfaces can be realigned to demonstrate 

they were at one time a single object. The physical fit can be viewed in two or three dimensions.

4.4 The absence of edge detail or material loss does not always rule out the possibility of a physical fit. A 

physical fit could result when physical features align across the separation boundary (e.g., striations, 

wood grain, printing). 

4.5 Different types of materials exhibit various types of individual characteristics based on their construction, 

chemical structure, and physical properties. The recognition and distinction between class and individual 

characteristics for different types of materials allows the use of the same general procedures for the 

physical fit examinations of all materials.

4.6 This guide contains a general procedure to perform physical fit examinations as well as a summary of 

considerations and limitations for an examiner to evaluate when conducting these examinations.

5. Significance and Use

5.1 This guide can assist the examiner in selecting and organizing a general analytical scheme for the 

evaluation and documentation of physical comparisons of materials for a potential physical fit. The type 

and size of material influences the exact steps and equipment needed to assess the physical fit.

Evaluation, documentation, and interpretation are all important parts of a physical fit examination. 

5.2 This guide addresses special considerations for physical fit analysis for glass, skeletal material, polymers, 

tapes and textiles. 

5.3 Foundations of physical fit examination in forensic science are described in the literature, including 

studies on the fractography of different materials and the use of physical fit examinations in forensic 

casework (1-7, 9,10,12-14).

5.4 It is not the intention of this guide to present comprehensive theories regarding the mechanism of 

fractures, tearing, cutting, or other methods of separation. This information is available from training 

courses and reference materials such as ASTM Guide C1256 and others (3 – 8). 

6. Quality Assurance Considerations

6.1 A quality assurance program is used to assess and verify that analytical testing procedures and reporting 

of results are monitored by means that include, but are not limited to, proficiency tests and technical 

audits. General quality assurance guidelines are available in ISO/IEC 17025. 

7. Apparatus and Materials 

7.1 Different equipment is used depending on the material being examined and the case specifics. 
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7.2 General list of common materials utilized:

7.2.1 Camera

7.2.2 Microscopes (e.g., stereomicroscope, comparison microscope)

7.2.3 Magnifier

7.2.4 Polarizing filters

7.2.5 Light box

7.2.6 Oblique lighting

7.2.7 Alternate light source(s)

7.2.8 Clay

7.2.9 Casting material

7.2.10 Plastic sheets

7.2.11 Scanners

7.2.12 Solvents 

7.2.13 Ruler

7.2.14 Micrometer

7.2.15 Sample handling tools (e.g., probe, forceps) 

7.2.16 Packaging and documentation materials (e.g., labels, markers)

7.2.17 Tape

8. Sample Handling

8.1 The general handling and tracking of samples should meet or exceed the requirements of Practice E1492 

and Guide E1459.

8.2 The need for multiple types of examinations (e.g., other trace, DNA, latent prints, firearms) is considered 

before initiating a physical fit examination. Communicate with examiners from other disciplines to 

coordinate the order of examination or evidence preservation and recovery methods, and document the 

communication as appropriate.

8.3 Physical fit examinations typically require that samples from more than one item of evidence be examined 

together. Documentation practices provide records of where samples came from and their condition as 

received in the laboratory. Document physical damage or the presence of other evidence. Documentation 

includes images, sketches, non-destructive marking/labeling of the individual samples, or other methods 

deemed appropriate for the evidence in question. 

8.3.1 Samples are uniquely identified prior to analysis. 

8.4 A preliminary examination of each sample is performed separately prior to bringing them into contact with 

each other to prevent cross-contamination. 

8.5 Carefully handle areas to be compared to protect them from damage or alteration.

8.6 Document alterations made to the evidence during the examination (e.g., cleaning, untangling).

8.7 Clean all tools used prior to contact with the evidence.

8.8 Repackage evidence in a manner to protect against damage or loss.

8.9 WARNING: Some samples have sharp edges and caution is warranted when handling these samples.

9. General Considerations and Limitations 

9.1 General Considerations:

9.1.1 The ductility of the object should be taken into consideration, especially in areas where stretching 

caused by the separation could cause distortion in a physical fit. Notes should include a discussion 

of apparent missing material and deformation of material that could impact results.

9.1.2 Features that carry across the separation boundary (e.g., scratches, stains, manufacturing defects) 

can be used to support a physical fit.

9.1.3 The separation method (e.g., cut, torn) can influence the features of a physical fit examination; 

however, specific damage assessment is outside the scope of this guide (e.g., E2225). 

9.1.4 Physical fit examination is a visual technique and therefore bias could occur. Precautions to 

minimize bias have been reported in the literature (15 - 17) and can include: 

9.1.4.1 Receiving adequate training on physical fit examinations including cognitive bias and 

methods that can mitigate or help avoid the effects of biasing information and procedures 
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9.1.4.2 Avoiding contextual bias (e.g., management of task irrelevant case information such as 

suspect’s confession or investigator’s opinions)

9.1.4.3 Assessing questioned samples separately prior to comparison to known samples

9.1.4.4 Employing a quality assurance program that complies with International Standards such as 

ISO 17025.

9.1.4.5 Conducting technical review and verification

9.1.5 Published studies addressing error rates for physical fit examination have been conducted, however 

they are not generalized and do not represent all associated variables (e.g., variety of materials, 

different separation mechanisms) (2,10,13,14).

9.1.6 In the absence of a physical fit, a sample cannot be associated with an individual source; however 

the possibility of a class association or exclusion could be determined with further examinations. 

When further examinations are conducted, refer to appropriate ASTM standards (e.g., E1610, 

E2225, E3260). 

9.2 Limitations

9.2.1 Sample composition or condition could limit a physical fit examination. Examples include, but are 

not limited to:

9.2.1.1 Size

9.2.1.2 Environmental effects

9.2.1.3 Wear

9.2.1.4 Deformation or stretching before separation 

9.2.1.5 Lack of features to compare along the separated edge(s)

9.2.1.6 Improper collection, preservation, or handling

10. General Procedure

10.1 Refer to Section 8 for sample handling considerations prior to and during physical fit examinations and 

Section 13 for results and interpretations.

10.2 A typical scheme for physical fit examinations is outlined in Figure 1. 

10.3 During the examination, questioned samples should be assessed separately prior to comparison to 

known samples. 

10.4 When exclusionary differences are observed at any point during the examination, no further 

examinations are required. Exclusionary differences can include differences in class characteristics (e.g., 

two pieces of tape with different construction or a red shirt with a piece missing compared to a blue 

piece of fabric). 

10.5 When the macroscopic contours do not align and there are no corresponding features on the separated 

surfaces or no traversing surface features, no further physical fit examinations are required. Additional 

physical and chemical analyses could be completed and are outside the scope of this guide.

10.6 Written or typed descriptions, sketches, photographs, scans, or other images are used to document each 

sample’s features. See Section 12 for additional detail on Examination Documentation.

10.7 A macroscopical assessment is conducted on the samples of interest.

10.7.1 The condition, general features, and properties of the samples are examined. Features such as 

material type, color, shape, construction features, curvature, fluorescence, surface features, 

texture, grain, weave, orientation, and degree of gloss are observed and documented. These 

features can be examined with various light sources at varying angles of illumination. The 

material of interest dictates what properties are present and relevant during the physical 

assessment.

10.7.1.1 Samples that are suitable for physical fit examination have features that are not 

noticeably obstructed by distortion, wear, weathering, or loss of material.

10.7.1.2 If the samples are deemed suitable for physical fit comparison, the samples are 

compared side by side and the macroscopic edge features are observed.

10.7.1.3 If the samples are deemed not suitable for physical fit comparison, no further physical 

fit analysis is required. Additional physical and chemical analysis could be warranted;

refer to appropriate ASTM standards (e.g., E1610, E2225, E3260).
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10.7.2 The macroscopic features on the separated edges, such as the presence of layers, continuous 

construction or manufacturing marks, fracture marks, alignment of the fracture pattern(s), color, 

dimensions, stains, or pattern continuation are observed and documented.

10.7.3 The dimensions of the questioned and known samples, in addition to the area of the alignment, 

can be measured (e.g., using a ruler, caliper, micrometer) and documented. 

10.8 When individual characteristics are not visible at the macroscopic level to support a physical fit, 

detailed observation at the microscopical level follows.

10.9 A microscopical examination is conducted on the samples of interest.

10.9.1 The microscopic edge features are observed using a simple magnifier, stereomicroscope, 

comparison microscope, or a combination thereof. Different lighting could be used depending on 

the type of material being examined (e.g., annular ring light, fiber optic light, transmitted light, 

reflected light). The size and physical properties of the samples determine which observation 

techniques should be used.

10.9.2 The edges of the questioned and known samples are compared microscopically for the 

observation and documentation of similarities and differences in features such as alignment, 

fracture pattern features, stretching, distortion, fracture marks, pigmentation, grain, texture, 

weave, twist, fluorescence, traversing surface features (e.g., scratches, stains), and missing 

material. Minimizing contact between the sample edges can prevent damage or contamination 

during alignment.

10.9.3 Optional: The portions of the edges that align across the samples (e.g., duct tape scrim edges) are 

measured and documented. 

10.10 A physical fit determination occurs when the samples share class and individual macroscopic and 

microscopic features across the aligned edges and surfaces, including the cross section. 

10.11 The samples or documentation of features are submitted for verification, technical review or both. 

10.11.1 To facilitate verification, the portion of the edge that aligns across the items should be 

measured (e.g., relative length, qualitative or quantitative descriptors, images with scale or 

magnification) and documented (2, 9, 10).

10.12 The correspondence of observed class characteristics between the compared items during a physical fit 

examination could warrant additional testing to evaluate the possibility of an association of the evidence 

with class characteristics or an exclusion (i.e., elimination). When further examinations are conducted, 

refer to appropriate ASTM standards (e.g., E1610, E2225, E3260) as well as the OSAC Guide for 

Interpretation and Reporting in Forensic Comparisons of Trace Materials. 

11. Special Considerations

11.1 The types of materials listed below are commonly encountered for physical fit examinations; however, 

this does not preclude other materials from being examined and compared for physical fits. For each 

material, class characteristics including composition or construction, the manner of separation, relevant 

features, and limitations inherent to that material are considered. Note that examples of characteristics 

and features are listed in each section but are not meant to be exhaustive. Different materials will 

exhibit varied individual characteristics based on their construction and chemical structure (amorphous, 

crystalline, fibrous or combinations thereof) or their properties (brittle or ductile). The recognition and 

distinction between class and individual characteristics for different materials allows the use of the same 

general procedures for the physical fit examinations of all materials.

11.2 Glass

11.2.1 Background: Glass exhibits brittle behavior at room temperature. Therefore, broken glass is 

particularly well suited for reassembly to its original configuration because there is usually no 

distortion caused by the breaking event (1).. The reassembled object will have the same shape 

as before the breaking event. For a more detailed description of glass fractography, see ASTM 

C1256, (1) and (3).

11.2.2 Separation methods: Glass objects deform elastically (i.e., reversibly) under an applied load 

until the onset of cracking, at which time the deformation is permanent (3). Fractures begin at 

a particular site (i.e., origin of impact) and grow from there. Cracks could develop slowly over 
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a period of time or rapidly. Crack development is dependent upon numerous factors including 

glass type, loading pressure, impact type (i.e., high or low velocity), or humidity (3).

11.2.3 Relevant features: Glass physical fit examinations involve conducting examinations of 

fracture surfaces for features such as rib marks, including arrest lines, Wallner lines, hackle 

marks, and scarps. Surface features, curvature, type of glass (e.g., tempered), color, thickness, 

and fluorescence are assessed to determine if all pieces could be from a single object. Surface 

features are also used to place all the fragments in the same orientation (e.g., fluorescent side 

facing up, surface scratches). 

11.2.4 Other considerations: There are no published studies addressing minimum lengths of fractured 

edges suitable for physical fit determinations. However, successful results from proficiency 

testing have been documented for glass fragments as small as approximately 5mm (11).

11.2.5 Other limitations: 

11.2.5.1 Examinations could be severely restricted due to improper collection and 

preservation at the scene or during transport.

11.2.5.2 Glass could shatter into multiple pieces rather than separating into only two pieces. 

In this case, reconstruction of pieces from a single evidentiary sample could be 

performed prior to a physical fit examination.

11.2.5.3 Tempered glass objects could leave fewer discriminating fracture features to conduct 

a physical fit examination due to the breaking mechanism.

11.3 Skeletal Material

11.3.1 Background: Physical fit examinations for skeletal material are generally conducted to 

reconstruct fragments in order to identify the origin of bone fragments, to conduct trauma 

examination, or to conduct morphological or metric assessment for biological profile 

estimations. In rare cases, however, a comparison between two items is conducted, such as in 

cases where material is recovered from different spatial locations, or at different temporal 

periods. In these cases, application of the results and interpretation terminology in this 

guideline could be appropriate.

11.3.2 Separation methods: The pattern of alterations to fresh bone depends upon the type of stress

applied to the material. Application of a low-velocity impact could lead to permanent plastic 

deformation of the material prior to material failure (fracture), leading to warping of the 

material. Higher velocity impact (e.g., gunshots) could cause material failure without prior 

plastic deformation. For dry bone (postmortem alterations), plastic deformation generally 

does not occur prior to breakage, potentially allowing easier reconstruction.

11.3.3 Relevant features:. Relevant features include alignment of separated edges, and consistency 

of both external compact bone and internal trabecular bone patterns.

11.3.4 Other considerations: Consideration should be given to the possibility that separated portions 

of skeletal material could undergo differing taphonomic processes after separation (e.g., 

differential weathering, burning).

11.3.5 Other limitations: Limitations include edge wear from mishandling or taphonomic processes,

plastic deformation of fresh bone, and straight fracture or breakage patterns.

11.4 Synthetic Polymers 

11.4.1 Background: Synthetic polymers are manufactured materials that are found in a variety of 

consumer and industrial products and are commonly encountered as items of evidence. For 

purposes of physical fit examination, synthetic polymers are classified as either “rigid” or 

“flexible”.

11.4.1.1 Examples of products made from rigid polymers include plastic vehicle parts, 

automotive paint chips, closed-cell foams, and other rigid polymeric materials 

excluding glass (see Glass section above).

11.4.1.2 Examples of products made from flexible polymers include plastic bags, garbage 

bags, cling film, some architectural paint, open cell foams, and other flexible 

polymeric materials excluding tape (see Tape section below). 

11.4.2 Separation methods: The fracture behavior of a polymer is either determined by the absence 

of appreciable plastic deformation prior to failure (i.e., brittle fracture) or the presence of 
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plastic deformation prior to failure (i.e., ductile fracture). Rigid polymers most often 

experience brittle fracture, while flexible polymers most often experience ductile fracture. 

This is due to their intrinsic properties (e.g., size, shape, composition, degree of crystallinity). 

However, external factors (e.g., temperature, state of wear, presence of existing damage, and 

amount, type, and orientation of applied stress) could cause variation in the brittle/ductile 

fracture behavior of a polymeric material.

11.4.2.1 Examples of the external factors that commonly cause fracture in rigid polymers 

include motor vehicle collision, bullet penetration, and blunt impact of a 

weapon/tool. 

11.4.2.2 Examples of the external factors that commonly cause fracture in flexible polymers 

include cutting, tearing, shearing with a tool or dispenser, or a combination of these.

11.4.3 Relevant features: Physical features of rigid and flexible synthetic polymers are assessed at a 

macroscopical level and microscopical level, as appropriate.

11.4.3.1 Relevant features in rigid polymer physical fit examinations include layer structure 

(including the substrate when present), hackle marks, pre-existing scratches or 

cracks across the separation boundary, contour, curvature, and texture. The threedimensional structure of a fractured polymer is valuable in a physical fit 

comparison.

11.4.3.2 Relevant features in flexible polymer physical fit examinations include color, size, 

perforation pattern, construction (if applicable), texture, print, and contour. Class 

characteristics imparted during manufacturing (e.g., striations, pigment bands, and 

interference colored bands), individual characteristics (e.g., fisheyes, arrowheads, 

streaks, tiger stripes, and surface scratches) or both which cross the separation 

boundary could demonstrate a physical fit (12). 

11.4.4 Other considerations:

11.4.4.1 Rigid polymers could shatter into multiple pieces rather than separating into only 

two pieces. In this case, reconstruction of pieces from a single evidentiary sample 

could be performed prior to a physical fit examination.

11.4.4.2 Coatings or other materials with multiple layers could separate along the physical 

boundary between layers.

11.4.4.3 Rigid polymers fatigue over time due to exposure to physical stressors, 

environmental conditions, or both. Cracks could form in a polymer due to fatigue 

and could alter how easily the polymer fractures, the location of a future fracture, or 

both.

11.4.4.4 The use of a light box as well as polarizing films could assist with visualization of 

some of the relevant features in flexible polymer physical fit examinations, 

including interference colors.

11.4.5 Other limitations:

11.4.5.1 Flexible polymers can easily deform when they are rolled, stretched, or twisted. 

When performing a physical fit examination, the amount of deformation could 

negatively impact the ability to align two or more pieces.

11.4.5.2 Sometimes when flexible polymers are cut, there are insufficient individual 

characteristics visible to determine a physical fit.

11.5 Tape 

11.5.1 Background: There are a variety of tape products available in the market, and tape evidence 

could include one or more classes of tape. Tapes have at least two layers, a backing and a 

pressure-sensitive adhesive, formulated to meet the tape’s specific end-use. Some tapes, such 

as duct tapes, also contain a fabric reinforcement layer. The physical structure and chemical 

composition of tape influences the relevant features of the material for physical fit 

examinations. A more detailed discussion of the classes of tape and their components is found 

elsewhere (ASTM E3260).

11.5.2 Separation Methods: Tapes are typically separated from the main source either by tearing 

sections (e.g., by hand, using teeth), or cutting the tape (e.g., scissors, knife, tape dispenser, 
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other sharp tool). However, fragments of tape could also be separated during an explosion or 

other high impact event.

11.5.3 Relevant features for physical fit examinations of tapes:

11.5.3.1 The relevant features for physical fit examinations are dependent on the class of 

tape involved. Generally, the presence of letters or patterns or other manufacturing 

marks on tape samples could be relevant in the side-by-side comparison of tape 

evidence for physical fits.

11.5.3.2 Macroscopic features to observe include color, fluorescence, shape, construction 

features, surface features, external marks or debris, texture, weave, orientation, and 

degree of gloss. The general torn edge appearance is also a relevant feature, and 

could include straight, angled, wavy, or patterned edges.

11.5.3.3 Microscopic features of the separated edges that can be used for alignment include 

manufacturing marks (e.g., calendering marks) tape layers, and areas of parallel 

protrusions or indentations. Protruding scrim fibers could be observed in tapes that 

possess them.

11.5.4 Other considerations:

11.5.4.1 When used in the commission of a crime, tape is typically placed down on various 

substrates such as paper, wood, metal, or skin. There is also potential for the tape 

to adhere to itself. When collected, residues, leftover material, or additional forms 

of trace evidence (e.g., fibers, soil) from the original substrate could remain on the 

adhesive side of the tape. These residues could obstruct or interfere with the 

examination and documentation of features. In those situations, the examiner could 

attempt to separate the tape from the extraneous material using warm air, liquid 

nitrogen, a freezer, or solvents. However, the examiner should be careful to gently 

separate the tape under magnification to avoid damaging the ends or destroying 

features needed for physical fit examination, while preserving the extraneous 

material for other forensic examinations.

11.5.4.2 The presence and orientation of reinforcing material (such as in duct, cloth, or 

filament tapes) could be used to orient and compare similar items.

11.5.4.3 Some kinds of tape could feather at the edges, where only portions of the layers 

can separate, leaving microscopic features that are unlikely to be randomly 

reproduced.

11.5.4.4 Physical fit determinations of some tapes (e.g., duct tapes with thicker adhesives) 

can be facilitated by removing some of the adhesive layer. To prevent the 

distortion of the edge features and scrim alignment, part of the adhesive is 

carefully removed until the scrim fibers are visible. 

11.5.5 Other limitations:

11.5.5.1 Some classes of tape are more likely than others to deform from stretching (e.g., 

electrical tape) or to have loss of material (e.g., masking tape). In addition, tapes 

with fewer layers do not have as many potential features to observe for physical 

fit comparisons.

11.5.5.2 In an explosion, fire, or high-impact event, fragments of tape could be lost or 

partially destroyed, preventing a full comparison for physical fits.

11.5.5.3 Tape samples without the full width of tape present could limit physical fit 

evaluations.

11.6 Textiles

11.6.1 Background: Textiles are comprised of natural or manufactured fibers subjected to a variety 

of manufacturing processes (e.g., spinning, weaving, knitting) to produce complex 

materials such as cordage and fabric. Although on a basic level all textiles are formed 

from fibers, the final product can vary in color, construction, and composition. Physical 

fit examinations could be performed in cases where pieces of damaged cordage or 

fabric are recovered from various locations. 
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11.6.2 Separation Methods: Textile physical fits occur when cordage or fabric has 

been mechanically damaged through cutting, tearing, or a combination of both, and the 

resulting pieces/edges are realigned. The separation process is dependent on the mechanical 

properties as well as the type and orientation of stress being applied. Characteristics such as 

a neat and straight severance (typically associated with cutting damage) or a ragged/irregular 

severance (typically associated with tearing damage) could assist with physical fit

examination. 

11.6.3 Relevant features: Physical features of a textile are assessed at the fabric/cordage level, 

yarn level and fiber level, as appropriate. Textile features include size, shape, 

construction, yarn and fiber characteristics, stitched edges, selvedges, color, patterns, stains, 

unusual stretching or contours, and damage. In addition to general features such as pattern 

and color, mechanical separation of textiles typically results in a series of long and 

short yarns/fibers which could be used to orient and physically align the textiles of 

interest. Following the physical alignment, these “longs and shorts” are examined to ensure 

that their relative positions along the damaged edges of two or more textile pieces 

correspond. 

11.6.4 Other Considerations: Textiles are flexible materials that can be rolled, stretched, and 

twisted. Orientation of the textile at the time of damage could impact the location, 

pattern and type of mechanical separation incurred. Additionally, when the elasticity limit of 

the textile is exceeded, permanent deformation could occur. When performing a textile 

physical fit examination, these deformations could impact the ability to align two or 

more damaged textile pieces. 

11.6.5 Other limitations: Sometimes the ability to perform physical fit examinations on damaged 

textiles is limited by laundering/handling/distorted threads, contaminants such as blood, 

stretching or distortion of the textile during damage, and general wear effects.

12. Examination Documentation 

12.1 Documentation includes written or typed descriptions, imaging, sketches, non-destructive marking or

labeling of the individual items, or other methods deemed appropriate for the evidence in question. 

12.2 Documentation should include observations of physical damage and the presence of other evidence.

12.3 Written or typed descriptions, sketches, photographs, scans, or other images are used to document each 

sample’s features. Close-up images or photomicrographs are used to document the microscopic features.

12.4 Documentation should include specific apparatus and materials utilized in the physical fit examination.

12.5 Physical fits of evidential value require documentation of sufficient quality for technical review, 

verification, court presentations, or other visual demonstrations. This includes images of pertinent edges 

and observed features as well as the correspondence between the edges of the pieces showing the 

physical fit.

12.6 Document observations that support the absence of a physical fit. 

12.7 Image documentation should include a scale, an overall image with a scale for reference, or annotation 

of the magnification used. 

12.8 The examination notes include sufficient detail to support the interpretations and opinions such that 

another qualified practitioner could fully evaluate the details of the examination and consideration of 

limitations, and thus be able to evaluate the quality of the interpretation and opinion based on those 

notes or documentation.

12.9 Verifications are documented in the case record. The verification documentation includes, but is not 

limited to, the verifier’s identity, date of verification, the result, and exhibits examined. 

13. Results and Interpretations

The following results and interpretations can be reached with regards to physical fit examinations:

13.1 Physical Fit

13.1.1 The items that have been broken, torn, or separated exhibit physical features that realign in a 

manner that is not expected to be replicated. A physical fit can result when features realign 

along the compared edges or when features do not realign along the compared edges but there 
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10

are physical features present (e.g., striations, wood grain) which carry across the separation 

boundary and can themselves be realigned. 

13.1.1.1 Physical Fit is the highest degree of association between items. It is the opinion that 

the observations provide the strongest support for the proposition that the items were 

once joined together to form a single object as opposed to originating from different 

sources. 

13.1.1.2 A Physical Fit is not currently based upon a statistical evaluation of data; it is also 

not based upon exhaustive comparisons to all potential sources.

13.2 No Physical Fit

13.2.1 The items correspond in observed class characteristics, but exhibit physical features that do not 

realign, or they realign in a manner that could be replicated. 

13.2.2 Alternatively, the items can exhibit physical features that partially realign, display 

simultaneous similarities and differences, show areas of discrepancy (e.g., warped areas, 

burned areas, missing pieces), or have insufficient individual characteristics that hinder the 

ability to determine the presence or absence of a physical fit. 

13.2.3 The absence of a physical fit does not imply that the compared items originated from different 

sources. 

13.2.4 When no physical fit is observed and additional trace material examinations are completed, 

refer to OSAC Guide for Interpretation and Reporting in Forensic Comparisons of Trace 

Materials. 

13.2.5 When the physical fit examination is the terminal examination step, a statement is included 

explaining the reasons for not completing further examinations.

13.2.6 The two items did not originate from the same source (exclusion) when the items exhibit 

differences in their class characteristics. 

14. Report Wording Examples

The following are only examples and not intended to be exhaustive. Each laboratory determines the specific 

wording to be used in its reports. Additional examples of report wording can also be found in the OSAC Guide 

for Interpretation and Reporting in Forensic Comparisons of Trace Materials. 

14.1 Physical Fit

14.1.1 The Item 1 piece of tape and the free end of the Item 2 roll of tape physically corresponded 

with distinctive features of the torn edges. This serves as the basis for the opinion that Item 1 

and Item 2 were once part of a single object (Physical Fit).

14.1.2 Based on distinctive features of the torn edge of one end of the Item 1 piece of tape and the free 

end of the Item 2 roll of tape, Item 1 was observed to physically correspond with the end of 

Item 2. This serves as the basis for the proposition that the Item 1 piece of tape originated and 

was at one time part of the Item 2 roll of tape, as opposed to the proposition that it originated 

from and was a part of another used roll (Physical Fit).

14.2 No Physical Fit

14.2.1 The Item 1 car piece from the scene was examined and compared to the Item 2 bumper. The 

Item 1 car piece and the Item 2 bumper were similar in general appearance but did not 

physically fit back together (No Physical Fit). The absence of a physical fit does not imply that 

the compared items did not originate from the same source, and they do share sufficient class 

characteristics to warrant additional comparison examinations to evaluate the possibility of an 

association with class characteristics or an exclusion.

14.2.2 The Item 1 and Item 2 pieces of plastic do not realign to form one larger piece (No Physical 

Fit). However, they do share sufficient class characteristics to warrant additional comparison 
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11

examinations to evaluate the possibility of an association of evidence with class characteristics 

or an exclusion. The results of those examinations will be reported separately.

14.2.3 The Item 1 metal tip exhibited physical features that generally align with the Item 2 broken 

knife, however, there were also areas of discrepancy. Due to these similarities and differences, 

no physical fit was determined (No Physical Fit). They do however share sufficient class 

characteristics to warrant additional comparison examinations to evaluate the possibility of an 

association with class characteristics or an exclusion.

14.2.4 The tape in Exhibit 1 displayed a different color than the known tape roll in Exhibit 2. 

Therefore, the Exhibit 1 tape did not come from the known tape in Exhibit 2 (Exclusion).

15. Verifications

15.1 Physical fits of evidential value are verified by another qualified examiner. Other results (e.g., no 

physical fit, exclusion) may also be verified.

15.2 Verification can be in the form of review and examination of the actual evidentiary material or by 

reviewing the documentation (e.g., images) which clearly and objectively demonstrates the physical fit. 

15.3 Verification can be completed during the technical review process.

16. Additional Considerations

16.1 During a physical fit examination, it is possible to encounter items with features that attach in a manner 

that could be replicated.

16.1.1 Examples of this type of evidence include vehicle parts that snap together (e.g., mirror and 

mirror assembly), electrical components (e.g., USB drive and port), a pen and cap, or clothing 

items separated at the seam (e.g., coat and sleeve without tearing of the fabric).

16.1.2 Items which attach in this manner demonstrate class characteristics which are alike, but do not 

have a separation boundary and edge features to compare and evaluate as with physical fit 

determinations.

16.1.3 Report wording example

16.1.3.1 The Item 1 mirror from the scene was examined and compared to the Item 2 mirror 

housing to determine whether or not a physical fit exists. Based on the 

examinations conducted, the items are able to be attached; however, there are no 

individual characteristics present. Therefore, these items could have been at one 

time connected, or they each could have been connected to other similar objects 

(No Physical Fit).

16.1.4 Additional examinations could be conducted on items that attach in this manner; however, 

these examinations are specific to the material and are beyond the scope of this guide.

17. Keywords

Physical fit, physical match, fracture match, fracture fit

18. References

(1) Quinn GD. Fractography of Ceramics and Glasses, NIST Special Publication, 960-16e2, May 2016.

(2) Brooks E, Prusinowski M, Gross S, Trejos T. Forensic physical fits in the trace evidence discipline: a 

review. For Sci Int Vol 313, 2020. https://doi.org/10.1016/j.forsciint.2020.110349.

(3) Frechette VD. Failure Analysis of Brittle Materials, Advances in Ceramics, Vol 28, Westerville, Ohio: 

Wiley-American Ceramic Society, 1990.. 

(4) Becker WT, Shipley RJ. ASM Handbook, Volume 11: Vol. 11: Failure Analysis and Prevention. Materials 

Park, Ohio: ASM International, 2002.

(5) Hull D. Fractography: observing, measuring and interpreting fracture surface topography. Cambridge, 

U.K.: Cambridge University Press, 1999.

(6) Glass Fractures, Scientific Working Group for Materials Analysis, Forensic Science 
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Forensic Physical Fit Examination

12

Communications, Volume 7, No 1, January, 2005.

(7) Hearle JWS, Lomas B, and Cooke WD. Atlas of Fibre Fracture and Damage to Textiles 2

nd Edition Boca 

Raton, LA: CRC Press 2000.

(8) Taubin JM, Adof FP, Robertson. Examination of Damage to Textiles in: J. Robertson, M. Grieve (Eds.), 

Forensic Examination of Fibres, Second ed., London: Taylor & Francis, 1992.

(9) McCabe KR, Tulleners FA, Braun JV, Currie G, Gorecho EN. A quantitative analysis of torn and cut duct 

tape physical end matching, J For Sci 58 (2013) S34–S42.

(10)Prusinowski M, Brooks E, Trejos T. Development and validation of a systematic approach for the 

quantitative assessment of the quality of duct tape physical fits, For Sci. Int. 307 (2020). 

(11) http://forensic-testing.net/system/files/fts-13-pm_summary.pdf (accessed 03/27/2020).

(12)Von Bremen UG, Blunt LKR. Physical Comparison of Plastic Garbage Bags and Sandwich Bags, J For 

Sci, Vol 28, No 3, July 1983, pp. 664-654.

(13)Thomson GZ, Dawood V, Yu, T, Lograsso BK, Vanderkolk J, Maitra R, Meeker WQ, Basawros AF. 

Fracture Mechanics-Based Quantitative Matching of Forensic Evidence Fragments. Statistics 

Applications.arXiv:2106.04809

(14) van Dijk CD, van Someren A, Visser R, Sjerps M. Evidential value of duct tape comparison using 

loopbreaking patterns, Forensic Science International, S0379-0738(22)00008-1, doi:

https://doi.org/10.1016/j.forsciint.2022.111178

(15)Spellman, B.A., Eldridge, H., & Bieber, P. (2022). Challenges to reasoning in forensic science decisions. 

Forensic Science international: Synergy, 4, e100200. https://doi.org/10.1016/j.fsisyn.2021.100200

(16)Dror, I. E. (2020). Cognitive and human factors in expert decision making: Six fallacies and the 

eight sources of bias. Analytical Chemistry, 92(12), 7998-8004. 

https://dx.doi.org/10.1021/acs.analchem.0c00704

(17)Quigley-McBride, A., Dror, I.E., Roy, T., Garrett, B.L., & Kukucka, J. (2022). A practical tool for 

information management in forensic decisions: User Linear Sequential Unmasking- Expanded (LSU-E) 

in casework. Forensic Science International: Synergy, 4, e100216. 

https://doi.org/10.1016/j.fsisyn.2022.100216
Figure 1

PHYSICAL FIT 

(10.10)

No further fit analysis 

– additional physical 

and chemical analysis 

could be warranted.

Start

Exclusionary 

differences in 

general 

features? (10.4)

Yes

No

Assess for 

Suitability (10.7)

No further fit analysis 

– additional physical 

and chemical analysis 

could be warranted.

Not

Suitable

Observe and Compare 

Macroscopic Features 

(10.7)

Suitable

Visible differences

Observe and Compare 

Microscopic Features (10.9)

NO PHYSICAL FIT

Visible 

differences

Alignment and 

individual 

characteristics 

visible? (10.8)

No visible

differences

PHYSICAL FIT 

(10.10)

Yes No

No visible

differences

EXCLUSION

(ELIMINATION)

Alignment and 

individual 

characteristics 

visible? (10.9)

Yes

No

Exclusionary 

differences? 

EXCLUSION

(ELIMINATION)

Yes

No