OSAC 2022-S-0038 Standard for Feature 

Selection in Friction Ridge Examination

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OSAC 2022-S-0038 

Standard for Feature 

Selection in Friction Ridge 

Examination

Friction Ridge Subcommittee

Physics/Pattern Scientific Area Committee

Organization of Scientific Area Committees (OSAC) for Forensic Science
OSAC 2022-S-0038 Standard for Feature 

Selection in Friction Ridge Examination

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OSAC Proposed Standard

OSAC 2022-S-0038 

Standard for Feature Selection in

Friction Ridge Examination

Prepared by 

Friction Ridge Subcommittee

Organization for Scientific Area Committees (OSAC) for Forensic Science

Version: 2.0

August 2023

Disclaimer:

This OSAC Proposed Standard was written by 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 (STR). The STR process is vital to OSAC’s mission of 

generating and recognizing scientifically sound standards for producing and interpreting forensic 

science results. The STR 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 STR 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 
OSAC 2022-S-0038 Standard for Feature 

Selection in Friction Ridge Examination

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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-forensicscience/scientific-technical-review-panels
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Table of Contents

1. Introduction ....................................................................................................................... 1

2. Scope ................................................................................................................................. 1

3. Terms and Definitions....................................................................................................... 2

4. General Requirements ....................................................................................................... 3

4.1.1. Ridges.......................................................................................................................... 3

4.1.2. Minutiae....................................................................................................................... 4

4.1.3. Incipient Ridges........................................................................................................... 5

4.1.4. Dissociated Ridges...................................................................................................... 6

4.1.5. Ridge flow ................................................................................................................... 7

4.1.6. Pattern Elements – Recurves and Triradii................................................................... 7

4.1.7. Regular Creases........................................................................................................... 8

4.1.8. Irregular Creases.......................................................................................................... 9

4.1.9. Wrinkles .................................................................................................................... 10

4.1.10. Scars.................................................................................................................. 11

4.1.11. Unstable features............................................................................................... 12

4.1.12. Shape of the Impression.................................................................................... 12

5. General Recommendations.............................................................................................. 13

5.1.6.1. Ridges ............................................................................................................... 14

5.1.6.2. Minutiae ............................................................................................................ 14

5.1.6.3. Incipient Ridges................................................................................................ 15

5.1.6.4. Dissociated Ridges............................................................................................ 15

5.1.6.5. Ridge flow......................................................................................................... 16

5.1.6.6. Pattern Elements – Recurves and Triradii ........................................................ 16

5.1.6.7. Regular Creases ................................................................................................ 16

5.1.6.8. Irregular Creases............................................................................................... 17

5.1.6.9. Wrinkles............................................................................................................ 18

5.1.6.10. Scars.................................................................................................................. 18

5.1.6.11. Unstable features............................................................................................... 18

5.1.6.12. Shape of the Impression.................................................................................... 19

6. Appendix A: Ridges ........................................................................................................ 22

7. Appendix B: Minutiae ..................................................................................................... 23

8. Appendix C: Incipient Ridges ......................................................................................... 28

9. Appendix D: Dissociated Ridges..................................................................................... 30
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10. Appendix E: Ridge Flows................................................................................................ 32

11. Appendix F: Pattern Elements – Recurves and Triradii.................................................. 33

12. Appendix G: Regular Creases ......................................................................................... 35

13. Appendix H: Irregular Creases and Wrinkles.................................................................. 38

14. Appendix I: Scars ............................................................................................................ 40

15. Appendix J: Unstable Features........................................................................................ 41

16. Appendix K: Shape of Impression................................................................................... 42

17. Appendix L: Feature Sets and Relationships – Search Diagnosticity and Source 

Diagnosticity........................................................................................................................... 44

18. Appendix M: Quick Reference Summary Table ............................................................. 45

19. Appendix N: References.................................................................................................. 48

20. Appendix O: Change Log................................................................................................ 50
OSAC 2022-S-0038 Standard for Feature 

Selection in Friction Ridge Examination

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1. Introduction

1.1. This standard has been developed with the objective of improving the quality and 

consistency of friction ridge examination practices. 

1.2. This standard provides a comprehensive list of features and their definitions which may be 

used during the friction ridge examination process. The features expand on those provided 

by the Extended Feature Set Detailed Instructions in American National Standard for 

Information Ssytems; “Data Format for the Interchange of Extended Friction Ridge 

Features”; ANSI/NIST-ITL 1-2011 (Update:2015), NIST Special Publication 500-290 

Edition 3 (2015). 

1.3. This standard also includes information about the diagnosticity and factors affecting the 

appearance of the features. The diagnostic value of each feature is based on the consensus 

opinion of the OSAC Friction Ridge Subcommittee. Limited scientific literature is 

referenced, where applicable; however, empirical measures of the rarity of each feature 

type or combinations of feature types have not been well established within each section 

of the friction ridge skin or across different populations.

1.4. In addition to the significance of each feature, this standard provides an awareness of the 

relationship among features that can be used during examination.

1.5. Section 4 specifies the list of features and their definitions. Section 5 provides information 

about the diagnosticity and factors affecting the appearance of the features. The appendices 

provide additional information and images depicting the features described in this standard. 

1.6. Images depicting friction skin in the figures throughout this standard are reprinted with 

permission from the Journal of Forensic Identification.

1.7. In this standard, the following verbal forms are used: “shall” indicates a requirement, 

“should” indicates a recommendation; “may” indicates permission; and “can” indicates a 

possibility or capability.

2. Scope

2.1. This standard specifies the features that can be utilized during friction ridge examinations

and provides guidance regarding factors affecting the distortion and diagnosticity of those 

features.

2.2. This standard does not address the examination methodology or documentation.
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3. Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

3.1. Attributes: Components of features that can be measured or counted.

3.2. Examination: The act or process of observing, searching, detecting, recording, 

prioritizing, collecting, analyzing, measuring, comparing, and/or interpreting.

3.3. Examiner (Friction Ridge)/Competent Friction Ridge Examiner: An individual who has 

successfully completed their FSP’s training program and has demonstrated to the FSP 

that they possess the knowledge, skills and abilities to perform the tasks required of their 

current position. An individual authorized to conduct friction ridge examinations for the 

FSP by observing and interpreting data, making decisions, forming conclusions and 

opinions, issuing reports and/or providing testimony.

3.4. Friction Ridge Features: Structures of the friction ridge skin, as observed in the skin or 

recorded and observed in an impression. The set of observed data used to compare and 

interpret similaritities or differences between a questioned impression and the exemplar 

prints of a donor. Similarities are features that an examiner interprets to be in 

correspondence between a questioned print and a region within the exemplar prints of a 

donor. An examiner’s interpretation of differences between a question print and 

exemplar prints of a donor generally leads at attributing the differences to one of two 

causes: 1) the questioned print and exemplars prints were made by different sources or 

2) the questioned print and the exemplars were likely made by the same donor but are 

displaying variation in appearance due to the limits of persistency of features or 

distortion factors. 

3.5. Pattern force area: A region of friction ridge skin in which minutiae form in a predictable 

density and orientation due to the influence of nearby ridges [19.1, 19.2, 19.3]. 

3.6. Rarity (of a feature type): The frequency for which a type of feature is encountered in a 

group of people (its prevalence), either in isolation or in conjunction with other 

information about its local context. 

3.7. Search Diagnosticity: The usefulness of a feature (or features) to limit the comparisons 

to specific anatomical regions within the hands or feet, left or right hands or feet, or 

specific orientations [19.3, 19.4, 19.5].

3.8. Source: an individual from which an item (e.g. crime scene impression) originates.

3.9. Source Diagnosticity: The usefulness of a feature (or features) to include or exclude a 

potential donor [19.3, 19.4].
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4. General Requirements

4.1. Examiners shall use only those features and their associated attributes included on the 

following list during friction ridge examinations to support suitability determinations 

and source conclusions. Other aspects of impressions of friction ridge skin may be used 

to aid in the interpretation of the features and their attributes (e.g., shape and smearing of 

the impression can indicate the impact of torque during contact, causing differences in 

the curvature of the ridges).

NOTE: Although the features are defined in relation to the skin, different features can 

manifest in an impression of the skin in ways that are not easily discernible or 

distinguishable [19.3].

4.1.1. Ridges: 

The ridges are the primary feature type in the friction ridge skin. The ridges are 

the fully formed elevated papillary rows of skin on the volar surfaces of normal 

human hands and feet. If the friction ridge skin is considered a topographical map, 

the ridges are typically the feature at the highest elevation and are the main 

contact regions when the friction ridge skin touches a surface. On the skin, fully 

formed ridges can be distinguished from incipient ridges by the existence of sweat 

pores spaced somewhat evenly along the path of the ridge. See Appendix A for 

examples of ridges and ridge attributes.

4.1.1.1. Attributes:

4.1.1.1.1. Number – count of ridges within a region of skin or within an 

impression of the skin.

4.1.1.1.2. Ridge Width – distance between the edges of a ridge at a given 

location on the ridge.

4.1.1.1.3. Furrow Width – distance between the edges of adjacent ridges at a 

given location on the ridges.

4.1.1.1.4. Length – distance between two locations along the path of a ridge.

4.1.1.1.5. Spacing – distance between the midpoints of two adjacent ridges.

4.1.1.1.6. Direction – angle of the path of a ridge in relation to a fixed point 

in the skin or impression (e.g., a ridge that is perpendicular to an 

irregular crease).

4.1.1.1.7. Curvature – change in angles along the path of a ridge for a given 

segment of the ridge.
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4.1.1.1.8. Edge Shape – contour of the edge of a ridge (straight, protrusion, 

and intrusion).

4.1.1.1.9. Pore Position – location of a pore with respect to the edge of the 

ridge or another pore.

4.1.1.1.10. Open Field – four or more adjacent and continuous ridges with a 

visible length of at least 3mm where no minutiae are present within 

an area of skin.

4.1.2. Minutiae: 

A minutia defines the end of a ridge and is the primary landmark within the 

ridged skin used by examiners and biometric systems. A ridge can end in three 

different manners: 1) no connection to the adjacent ridge above the level of the 

furrow (i.e., ending ridge), 2) completely connected to the adjacent ridge from the 

bottom of the furrow to the top of the ridge (i.e., bifurcation) or 3) partially 

connected to the adjacent ridge (i.e., ambiguous minutiae). The manner in which a 

ridge ends can change during adolescent growth as the cells of the skin rapidly 

multiply to keep pace with the growing hand or foot [19.3, 19.6]. Additionally, 

the connectors between two ridges can change as a result of the aging process

[19.3, 19.6]. See Appendix B for examples of minutiae and minutiae attributes.

4.1.2.1. Attributes:

4.1.2.1.1. Number – count of minutiae within a region of skin or within an 

impression of the skin.

4.1.2.1.2. Density – number of minutiae within a specified surface area (e.g., 

per mm2).

4.1.2.1.3. Orientation – direction of the path(s) of the ridge(s) emanating 

from a minutia in relation to a fixed point in the skin or impression.

4.1.2.1.4. Connectedness – extent to which the end point of one ridge 

segment is joined or linked to a neighboring ridge.

4.1.2.1.5. Compound Minutiae – the combination of multiple minutiae within 

a close proximity or that manifest as a single structure. Compound 

minutiae might include the following: short ridge, dot, break, 

enclosure, overlap, spur, crossbar, bridge, opposing bifurcations, 

dock, ending ridge plus bifurcation combination, 

trifurcation/double bifurcation, return, and merge point [19.2, 19.3, 

19.7, 19.8, 19.9]. See Table 3 in Appendix B for examples of 

compound minutiae.
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4.1.2.1.6. Pattern Force Minutiae – Minutiae that form in a pattern force area 

bearing a direction consistent with the majority of minutiae in that 

area.

4.1.2.1.7. Counter Pattern Force Minutiae – Minutiae that form in a pattern 

force area bearing a direction not consistent with the majority of 

minutiae in that area.

4.1.3. Incipient Ridges: 

Incipient ridges are raised papillary ridges that are typically lower in elevation 

than the mature ridges (Section 4.4.1). Incipient ridges occupy space in the 

furrows, between the mature ridges. Unlike the mature ridges, incipient ridges do 

not have sweat pores. Incipient ridges are typically less than one half the average 

width of the surrounding mature ridges and often display numerous breaks. The 

incipient ridges often continue to manifest as people age [19.3, 19.6, 19.10., 

19.11]. Incipient ridges can fuse to each other or to the ends of mature ridges and 

can approach the height and width of the mature ridges [19.3, 19.6]. See 

Appendix C for examples of incipient ridges and incipient ridge attributes.

4.1.3.1. Attributes:

4.1.3.1.1. Number – count of incipient ridges within a region of skin or 

within an impression of the skin.

4.1.3.1.2. Density – number of incipient ridges within a specified surface 

area (e.g., per mm2).

4.1.3.1.3. Width - distance between the edges of an incipient ridge at a given 

location on the incipient ridge

4.1.3.1.4. Length – distance between two locations along the path of an 

incipient ridge.

4.1.3.1.5. Direction – angle of the path of an incipient ridge in relation to a 

fixed point in the skin or impression (e.g., an incipient ridge that is 

perpendicular to an irregular crease).

4.1.3.1.6. Inter-Incipient Gap – distance between the ends of two incipient 

ridges (i.e., the separation between incipient ridges within a row of 

incipient ridges).

4.1.3.1.7. Edge Shapes – contours along the edges of an incipient ridge 

(straight, protrusion, and intrusion).
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4.1.4. Dissociated Ridges: 

Dissociated ridges are raised portions of the friction ridge skin that are broken 

into short, wavy or dotlike segments that may be completely disorganized or 

somewhat follow the ridge flow in a given region of skin [19.12]. Dissociated 

ridges are typically at the same elevation as any surrounding normal ridges and 

might or might not contain sweat pores. Dissociated ridges are also known as 

dysplasia. See Appendix D for examples of dissociated ridges and dissociated 

ridge attributes.

4.1.4.1. Attributes:

4.1.4.1.1. Number – count of ridge segments within a region of skin or 

within an impression of the skin.

4.1.4.1.2. Density – number of ridge segments within a specified surface area 

(e.g., per mm2).

4.1.4.1.3. Ridge Width – distance between the edges of a ridge segment at a 

given location on the segment.

4.1.4.1.4. Furrow Width – distance between the edges of adjacent ridges at a 

given location on the ridges.

4.1.4.1.5. Length – distance between two locations along the path of a ridge 

segment.

4.1.4.1.6. Spacing – distance between the midpoints of two adjacent ridges.

4.1.4.1.7. Direction – angle of the segment of a ridge in relation to a fixed 

point in the skin or impression (e.g., a segment that is 

perpendicular to the core of a loop).

4.1.4.1.8. Curvature – change in angles along the path of a ridge segment.

4.1.4.1.9. Edge Shape – contour of the edge of a ridge segment (straight, 

protrusion, indentation, and discontinuity).

4.1.4.1.10. Pore Position – location of a pore with respect to the edge of the 

ridge segment or another pore.

4.1.4.1.11. Connectedness – extent to which the end point of one ridge 

segment is joined or linked to a neighboring ridge.
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4.1.5. Ridge flow: 

Ridge flows are general paths of ridges commonly found in specific regions of the 

hands and feet that reflect the stresses on the surface of the skin caused by the 

growth of the hands and feet and the presence of the regular flexion creases at the 

time the ridges are forming. These ridge flows are not defined “pattern elements,” 

but useful during the examination process because they are predictive for each 

region of the hand and foot [19.3, 19.4, 19.5]. See Appendix E for examples of

ridge flows and ridge flow attributes.

4.1.5.1. Attributes:

4.1.5.1.1. Curvature – change in angles along a series of parallel ridges at a 

given location along a ridge flow.

4.1.5.1.2. Convergence – loss of ridges along a ridge flow, causing an overall 

decrease in the width of the ridge flow.

4.1.5.1.3. Divergence – gain of ridges along a ridge flow, causing an overall 

increase in the width of the ridge flow.

4.1.6. Pattern Elements – Recurves and Triradii: 

Pattern elements, and the relationships between pattern elements, are most often 

associated with the development of classification schemes for the digits, palms, 

and feet. In the examination of partial impressions, the presence of one or more 

pattern elements can provide anatomical reference points and can be used to 

reduce the number of potential donors of an impression [19.2, 19.3, 19.4, 19.5, 

19.13, 19.14, 19.15]. 

Pattern elements include triradii (singular “triradius”) and recurves. A triradius is 

a convergence of three ridge fields, which creates three distinct rays from the 

center of the convergence. A recurve is the portion of a ridge path where the ridge 

turns with an acute inner angle, reversing the direction of the ridge path and 

resulting in an approximately 120o- 180ochange. When a sequence of ridges 

makes a turn, the ridge with the acutest angle in the sequence is the recurve. The 

innermost recurve is often associated with the core in fingerprint pattern 

classification. [19.36, 19.37]. See Appendix F for examples of pattern elements 

and attributes as described in this standard.

4.1.6.1. Attributes:

4.1.6.1.1. Number – count of recurves and triradii within a region of the 

friction ridge skin or in an impression. 

4.1.6.1.2. Triradius Angle – angle formed by two rays of a triradius.
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4.1.6.1.3. Recurve Ridge Count – number of ridges enclosed by a recurving 

ridge.

4.1.6.1.4. Pattern Element Relationships – ridge counts, distance, or angles 

between recurves or triradius centers of two or more pattern 

elements.

4.1.6.1.5. Recurve Direction – Angle of the bisector of the recurve in relation 

to a fixed point in the skin or impression.

4.1.7. Regular Creases: 

The regular creases are those flexion creases which form prior to the friction ridges 

and prior to flexion of the hand or foot during embryological formation [19.16, 

19.17, 19.18]. Regular creases are tightly bound to the underlying palmar 

aponeurosis and ridges tend not to traverse through these creases. Regular creases 

are also referred to as primary creases or major creases. The five regular creases of 

the palm include: wrist crease, thenar crease, distal transverse crease, proximal 

transverse crease, and palmar digital creases. The only regular creases associated 

with the sole are the plantar digital flexion creases where the skin of the toe meets 

the sole. 

Thumbs and great toes typically have a distal interphalangeal crease located at the 

joint between the distal and proximal phalanges (there is typically no medial 

phalange in the great toe or thumb). The four remaining digits of the hands and 

feet typically have a distal interphalangeal crease located at the joint of the distal 

and medial phalanges. The four fingers of the hand typically have a proximal 

interphalangeal crease located at the joint of the medial and proximal phalanges. 

In the remaining four toes, it is common for the proximal interphalangeal crease 

to be poorly formed or missing. See Appendix G for a schematic of the regular 

creases of the hands and feet and examples of attributes of regular creases.

4.1.7.1. Attributes:

4.1.7.1.1. Number – count of regular creases within a region of skin or within 

an impression of a skin.

4.1.7.1.2. Configuration – organization of the regular crease as a single 

structure or a compound structure (e.g., the palmar digital crease of 

the middle finger is typically a double crease while the palmar 

digital crease of the index finger is typically a single crease).

4.1.7.1.3. Spacing – distance between the midpoints of two regular creases.
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4.1.7.1.4. Position – location of a regular crease within the structure of the 

hand or foot.

4.1.7.1.5. Width – distance between the edges of a regular crease at a given 

location on the regular crease.

4.1.7.1.6. Length – distance between two locations along the path of a 

regular crease.

4.1.7.1.7. Curvature – change in angles along the path of a regular crease for 

a given segment of the crease.

4.1.7.1.8. Direction – angle of the path of a regular crease in relation to a 

fixed point in the skin or impression (e.g., a crease that is parallel 

to the direction of the surrounding ridges).

4.1.7.1.9. Edge shapes – contours of the skin contained within a regular 

crease.

4.1.7.1.10. Branching – diverging pattern of smaller creases along a regular 

crease.

4.1.8. Irregular Creases: 

The irregular creases are those flexion creases which form during or after ridge 

formation (ridges typically traverse through these creases) [19.16, 19.17, 19.18]. 

Although not as deep as the regular creases, the irregular creases also have 

attachments to the underlying structure of the hand or foot. Biologically, irregular 

creases are distinct from wrinkles; however, in impressions of friction ridge skin, 

irregular creases and wrinkles both tend to record as a linear void dissecting the 

ridges. Irregular creases are also referred to as secondary creases or minor

creases. The irregular creases show greater variability than the regular creases 

within the human population. See Appendix H for examples of irregular creases

and attributes of irregular creases.

4.1.8.1. Attributes:

4.1.8.1.1. Number – count of irregular creases within a region of skin or 

within an impression of a skin.

4.1.8.1.2. Density – number of irregular creases within a specified surface 

area (e.g., per mm2).

4.1.8.1.3. Width – distance between the edges of an irregular crease at a 

given location on the irregular crease.
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4.1.8.1.4. Length – distance between two locations along the path of an 

irregular crease.

4.1.8.1.5. Curvature – change in angles along the path of an irregular crease 

for a given segment of the crease.

4.1.8.1.6. Direction – angle of the path of an irregular crease in relation to a 

fixed point in the skin or impression (e.g., a crease that is parallel 

to the direction of the surrounding ridges).

4.1.8.1.7. Branching – diverging pattern of smaller creases along an irregular 

crease.

4.1.8.1.8. Angle of intersection – angle(s) created by the intersection of two 

or more irregular creases.

4.1.8.1.9. Spacing – distance between the midpoints of two irregular creases.

4.1.9. Wrinkles: 

Wrinkles are a result of a breakdown in the skin over time. The disorganization of 

the various fibers and large proteins in the dermis causes the dermis to fold 

inward, causing a crimp in the epidermis [19.12, 19.19]. Unlike the regular and 

irregular creases, wrinkles do not have dedicated attachments to the underlying 

structure of the hand or foot. In impressions of friction ridge skin, wrinkles and 

irregular creases both tend to record as a linear void dissecting the ridges. See 

Appendix H for examples of wrinkles and wrinkle attributes.

4.1.9.1. Attributes:

4.1.9.1.1. Number – count of wrinkles within a region of skin or within an 

impression of a skin.

4.1.9.1.2. Density – number of wrinkles within a specified surface area (e.g., 

per mm2).

4.1.9.1.3. Width – distance between the edges of a wrinkle at a given 

location on the wrinkle.

4.1.9.1.4. Length – distance between two locations along the path of a 

wrinkle.

4.1.9.1.5. Curvature – change in angles along the path of a wrinkle for a 

given segment of the wrinkle. 
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4.1.9.1.6. Direction – angle of the path of a wrinkle in relation to a fixed 

point in the skin or impression (e.g., a wrinkle that is parallel to the 

direction of the surrounding ridges).

4.1.9.1.7. Branching – diverging pattern of smaller wrinkles along a wrinkle.

4.1.9.1.8. Angles of intersection – angle(s) created by the intersection of two 

or more wrinkles.

4.1.9.1.9. Spacing – distance between the midpoints of two wrinkles.

4.1.10. Scars: 

A scar is a disfiguration of the skin as a result of wound healing [19.19, 19.20, 

19.21]. The disfiguration can occur in varying degrees dependent on the amount 

of skin contraction experienced at the site of the injury and medical intervention 

(e.g., stitches). Some scars are imperceptible, while others are dramatic. 

Additionally, scars initiated by temperature and chemical burns tend to disfigure 

the skin differently than cuts or punctures. Simple, linear scars tend to exist at a 

lower elevation than the tops of the ridges. Complex scars and scars that contain 

epithelial islands can exist at the same or higher elevation than the normal ridges. 

See Appendix I for examples of scars and scar attributes.

4.1.10.1. Attributes:

4.1.10.1.1. Number – count of scars within a region of skin or within an 

impression of a skin.

4.1.10.1.2. Width – distance between the edges of a scar at a given location on 

the scar.

4.1.10.1.3. Length – distance between two locations along the path of a scar.

4.1.10.1.4. Surface Area – measure of the total area of the surface the scar 

occupies.

4.1.10.1.5. Curvature – change in angle along the path of a scar for a given 

segment of a scar.

4.1.10.1.6. Direction – angle of the path of a scar in relation to a fixed point in 

the skin or impression (e.g., a scar that is perpendicular to the 

direction of the surrounding ridges).

4.1.10.1.7. Created Minutiae – new minutiae created at the border of a scar 

due to the misalignment of the original ridges during the healing 

process.
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4.1.10.1.8. Edge Shapes – contours defined by the border of a scar and any 

epithelial islands created as a result of the injury.

4.1.11. Unstable features: 

Unstable features are those features temporarily present in the skin as the result of 

wound healing or disease [19.12, 19.19, 19.22]. Unstable features include, but are 

not limited to, warts, eczema/psoriasis, actively healing injuries, calluses, and 

blisters. Depending on the nature of the unstable feature, it may exist lower, 

equal, or higher elevations than the tops of the main ridges. See Appendix J for 

examples of more common unstable features found in the friction ridge skin.

4.1.11.1. Attributes:

4.1.11.1.1. Number – count of unstable features within a region in the skin or 

impression.

4.1.11.1.2. Width – distance between the edges of an unstable feature at a 

given location on the unstable feature.

4.1.11.1.3. Length – distance between two locations along the path of an 

unstable feature.

4.1.11.1.4. Surface Area – measure of the total area of the surface the unstable 

feature occupies.

4.1.11.1.5. Curvature – change in angle along the path of an unstable feature 

for a given segment of the feature.

4.1.11.1.6. Direction – angle of the path of an unstable feature in relation to a 

fixed point (e.g., scrape that is parallel to the direction of the 

surrounding ridges).

4.1.11.1.7. Edge Shapes – contours of an unstable feature.

4.1.12. Shape of the Impression: 

The shape of an impression is generally dictated by the contact points between a hand or 

foot and a surface [19.3, 19.4, 19.6]. The shape of an impression is often a combination 

of outer borders and inner borders. The outer perimeter delineates the maximum surface 

area of contact between the hand/foot and the surface. Within the outer contact perimeter, 

inner borders can be created by the topology of the hand/foot (e.g., the mid-palm), the 

topology of the skin (e.g., regular creases), or movement on the surface (e.g., smears 

leading to the final stop position of a palm).
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The surface area and borders of an impression can help discriminate between potential 

donor regions of an impressions (e.g., a latent print that only needs to be compared to the 

interdigital region of the palms), isolate individual latent prints on a lift card or image, or

assess the completeness of exemplar prints (e.g., visible non-ridge skin border in an 

exemplar palm print ensure complete recording of the ridged skin). See Appendix K for 

examples of shape and shape attributes.

4.1.12.1. Attributes:

4.1.12.1.1. Surface Area – measure of the total area of the surface the 

impression occupies.

4.1.12.1.2. Outline – the contours along the border of the impression.

4.1.12.1.3. Non-Ridged Skin Border – the junction or transition between the 

ridged skin and the non-ridged skin.

5. General Recommendations

5.1. The diagnosticity of features should be considered when conducting friction ridge 

examinations and forming suitability determinations and source conclusions.

5.1.1. Diagnosticity, generally, refers to the usefulness of information to assist in a 

choice or decision. Diagnosticity of friction ridge features refers to the usefulness 

of the feature, or attribute of a feature, for establishing search parameters (Search 

Diagnosticity) or the usefulness of the feature for determining source (Source 

Diagnosticity).

5.1.2. Features that exhibit low levels of variation in the population can be used for 

establishing search parameters. Features with generally low variation include the 

following: shape of the impression, creases, pattern elements, and ridge flows. 

Conversely, those features that exhibit higher levels of variation in the human 

population are useful for distinguishing one finger, palm, toe, or foot from 

another. 

5.1.3. Pattern elements, ridge flows, and creases can be useful for excluding a given 

donor, however these features do not typically provide strong support for same 

source opinions. 

5.1.4. Features that exhibit higher levels of variation in the population can be used to 

support same source opinions. The most variable features in the population 

typically include the following: ridges, minutiae, incipient ridges, dissociated 

ridges, and certain attributes of creases. Acquired features (wrinkles, scars, 

unstable features) exhibit more complex diagnosticity, depending on the feature. 
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5.1.5. The overall search diagnosticity and source diagnosticity for a given impression is 

impacted by the totality of a specific combination of features and available feature 

attributes. Generally, as the number and diversity of features increase, the search 

and source diagnosticities also increase. Appendix L contains examples of how 

combinations of features can be used to determine diagnosticity. Appendix M 

provides a quick reference table of feature diagnosticity.

5.1.6. The diagnosticity for each of the features include the following:

5.1.6.1. Ridges: 

5.1.6.1.1. Search Diagnosticity:

5.1.6.1.1.1. The search diagnosticity for the ridges is generally low 

because all regions of the friction ridge skin are expected to 

have ridges.

5.1.6.1.2. Source Diagnosticity:

5.1.6.1.2.1. In general, as the surface area of an impression increases 

(ergo an increase in the number of ridges and the visible 

lengths of the ridges), the source diagnosticity of the 

impression also increases [19.3, 19.6, 19.23].

5.1.6.1.2.2. In general, as an open field increases in size (more ridges or 

longer visible lengths of the ridges), the source 

diagnosticity of the open field also increases.

5.1.6.2. Minutiae: 

5.1.6.2.1. Search Diagnosticity:

5.1.6.2.1.1. In regions where growth stresses “force” minutiae to form, 

there tends to be a high density of minutiae that share 

direction (the transition zone from the hypothenar into the 

mid-palm region is one such zone). This concept is called 

“pattern force”. [19.1, 19.2, 19.3] Pattern force areas can 

be used to narrow search parameters, which increase search 

diagnosticity of these minutiae.

5.1.6.2.2. Source Diagnosticity:

5.1.6.2.2.1. Minutiae type(s) and configurations can increase or 

decrease the source diagnosticity of the cluster of minutiae 

(e.g., in the distal portion of the fingers, bifurcations tend to 
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occur less frequently and therefore have higher source 

diagnosticity compared to ridge endings). [19.2, 19.8, 19.9]

5.1.6.2.2.2. Typically, as the surface area of skin represented in an 

impression increases, so too does the number of minutiae 

present within the impression. While the source 

diagnosticity of a cluster of minutiae typically increases as 

the number of minutiae increases, the source diagnosticity 

ranges at a given number of minutiae until a theoretical 

maximum threshold is achieved (e.g., a rolled fingerprint). 

Below this theoretical maximum threshold, source 

diagnosticity for a given cluster depends on anatomical 

region, the density of the minutiae, the influence of pattern 

force, the orientation of the minutiae, the distance between 

the minutiae, and the population of donors under 

consideration [19.2, 19.24, 19.25, 19.26, 19.27]

5.1.6.3. Incipient Ridges: 

5.1.6.3.1. Search Diagnosticity:

5.1.6.3.1.1. The search diagnosticity for incipient ridges is generally 

low because incipient ridges can appear throughout the 

friction ridge skin and, unlike the ridges and minutiae, are 

not generally subject to pattern force.

5.1.6.3.2. Source Diagnosticity:

5.1.6.3.2.1. In general, as the number of incipient ridges within an 

impression increases, the source diagnosticity of the 

impression also increases.

5.1.6.4. Dissociated Ridges: 

5.1.6.4.1. Search Diagnosticity:

5.1.6.4.1.1. The search diagnosticity for dissociated ridges is generally 

low because dissociated ridges can appear anywhere in the 

friction ridge skin.

5.1.6.4.2. Source Diagnosticity:

5.1.6.4.2.1. In general, as the number of dissociated ridges within an 

impression increases, the source diagnosticity of the 

impression also increases.
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5.1.6.5. Ridge flow: 

5.1.6.5.1. Search Diagnosticity:

5.1.6.5.1.1. The search diagnosticity of ridge flows is generally high 

because the ridge flows follow a predictable distribution in 

the human population for each region of the friction ridge 

skin. [19.3, 19.4, 19.5]

5.1.6.5.2. Source Diagnosticity:

5.1.6.5.2.1. Generally, the source diagnosticity of ridge flows is low. 

Ridge flows tend to show significant left/right symmetry 

within a person. This symmetry is more pronounced within 

the corresponding hands of monozygotic twins. [19.3]

5.1.6.6. Pattern Elements – Recurves and Triradii: 

5.1.6.6.1. Search Diagnosticity:

5.1.6.6.1.1. The search diagnosticity of pattern elements is generally 

high because patterns follow a predictable distribution 

within human populations for each region of the friction 

ridge skin. [19.2, 19.3, 19.5, 19.6, 19.8, 19.13, 19.14, 

19.15, 19.35]

5.1.6.6.2. Source Diagnosticity:

5.1.6.6.2.1. The source diagnosticity of pattern elements is generally 

low. Patterns tend to show significant left/right symmetry 

within a person. This symmetry is more pronounced within 

the corresponding hands of monozygotic twins. [19.15, 

19.25, 19.26]

5.1.6.6.2.2. The source diagnosticity of a pattern element or group of 

pattern elements depends on the population under 

consideration and the region of skin within which it resides. 

For instance, whorls are less common in the interdigital 

regions of palms than the interdigital regions of feet based 

on population frequencies in the United States. [19.13, 

19.14]

5.1.6.7. Regular Creases: 

5.1.6.7.1. Search Diagnosticity:
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5.1.6.7.1.1. The search diagnosticity of the regular creases is generally 

high because the regular creases follow predictable 

distributions within human populations for each region of 

the friction ridge skin. [19.28, 19.29]

5.1.6.7.2. Source Diagnosticity:

5.1.6.7.2.1. The source diagnosticity of the number, configuration, and 

position of the regular creases is generally low. These 

attributes tend to show significant left/right symmetry 

within a person. This symmetry is more pronounced within 

the corresponding hands of monozygotic twins. [19.30, 

19.31, 19.32]

5.1.6.7.2.2. The source diagnosticity of the width, length, curvature, 

and direction of the regular creases is low to moderate. 

These attributes often show significant left/right symmetry 

within a person and similarity within the corresponding 

hands of monozygotic twins. [19.30, 19.31, 19.32]

5.1.6.7.2.3. The source diagnosticity of the edge shapes and branching 

of a crease is expected to range from moderate to high. 

These attributes can show significant left/right symmetry 

within a person and similarity within the corresponding 

hands of monozygotic twins. [19.30, 19.31, 19.32]

5.1.6.8. Irregular Creases: 

5.1.6.8.1. Search Diagnosticity:

5.1.6.8.1.1. The search diagnosticity of the number, density, width, 

length, curvature, and direction of irregular creases depends 

on the region of skin under consideration. The search 

diagnosticity of these attributes is higher for thenars of 

palms, proximal and medial phalanges of the fingers, and 

the arches of the feet because a high density of creases is 

expected in these regions. Elsewhere in the friction ridge 

skin the irregular creases are more variable, and 

consequently less useful for search diagnosticity. [19.3]

5.1.6.8.2. Source Diagnosticity:

5.1.6.8.2.1. The source diagnosticity of the number, density, width, 

length, curvature, and direction of irregular creases depends 

on the region of skin considered. The source diagnosticity 

is lower for palm thenars, proximal and medial phalanges 
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of the fingers, and the arches of the feet because a high 

density of creases is expected in these regions. Elsewhere 

in the friction ridge skin the irregular creases are more 

variable, and consequently displaying higher source 

diagnosticity.

5.1.6.8.2.2. The source diagnosticity of the branching and angles of 

intersection of irregular creases is expected to range from 

moderate to high. These attributes can show significant 

left/right symmetry within a person and similarity within 

the corresponding hands of monozygotic twins. [19.30, 

19.31, 19.32]

5.1.6.9. Wrinkles: 

5.1.6.9.1. Search Diagnosticity:

5.1.6.9.1.1. The search diagnosticity for wrinkles is generally low 

because wrinkles can appear anywhere in the friction ridge 

skin.

5.1.6.9.2. Source Diagnosticity:

5.1.6.9.2.1. In general, as the number of wrinkles within an impression 

increases, the source diagnosticity of the impression also 

increases.

5.1.6.10. Scars: 

5.1.6.10.1. Search Diagnosticity:

5.1.6.10.1.1. The search diagnosticity for scars is generally low because 

scars can appear anywhere in the friction ridge skin.

5.1.6.10.2. Source Diagnosticity:

5.1.6.10.2.1. In general, as the number or complexity of a scar within an 

impression increases, the source diagnosticity of the 

impression also increases.

5.1.6.11. Unstable features: 

5.1.6.11.1. Search Diagnosticity:
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5.1.6.11.1.1. The search diagnosticity for unstable features is generally 

low because unstable features can appear anywhere in the 

friction ridge skin.

5.1.6.11.2. Source Diagnosticity:

5.1.6.11.2.1. In general, as the number or complexity of an unstable 

feature within an impression increases, the source 

diagnosticity of the impression also increases.

5.1.6.12. Shape of the Impression: 

5.1.6.12.1. Search Diagnosticity:

5.1.6.12.1.1. The search diagnosticity of size, outline, and non-ridged 

skin border of an impression is generally high because the 

size, contours, and skin type transitions of human hands 

and feet are generally shared in the population. [19.3, 19.6, 

19.33, 19.34]

5.1.6.12.2. Source Diagnosticity:

5.1.6.12.2.1. The source diagnosticity of the shape of an impression is 

low. Hands and feet tend to show significant left/right 

symmetry within a person and similarity within the 

corresponding hands of monozygotic twins.

5.2. Factors affecting the appearance of features should be considered when conducting 

friction ridge examinations and interpreting the features and their attributes.

5.2.1. Variation in the appearance of the features can originate from biological causes or 

the result of physical contact. Biological factors are those factors affecting the 

stability of the feature over time in the friction ridge skin (e.g., aging) or the 

typical development of the feature (e.g., syndactyly). Contact factors are those 

factors that can affect the appearance of the features when they are recorded in an 

impression. 

5.2.2. The following factors are common causes for features to vary in appearance over 

time or due to circumstances of touch. These factors are not meant to be 

exhaustive of all possibilities. 

5.2.2.1. Adolescent growth – growth of the hand or foot from the time the ridges 

form until adult size is attained (typically late teens).

5.2.2.2. Aging – changes in the friction ridge skin that take place because of the 

natural aging process; typically, these changes begin after the age of forty.
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5.2.2.3. Injury – physical damage to the hand, foot, or friction ridge skin that elicits 

a wound healing response (e.g., cut or burn); certain injuries can result in 

the formation of a scar.

5.2.2.4. Disease – disorder in the structure or function of the skin that produces 

specific signs or symptoms and is not related to a physical injury (e.g., wart, 

psoriasis, or acquired ridge aplasia).

5.2.2.5. Hand flexion – the degrees to which the digits can be flexed at the joints or 

the rotation of the thumb.

5.2.2.6. Abduction of digits – the degrees to which the digits can be spread apart 

from one another.

5.2.2.7. Angle of contact – the position of the hand or foot with respect to the surface

during contact.

5.2.2.8. Compressive stress – the squeeze of the skin between the bone structure of 

the hand or foot and a surface (also referred to as “deposition pressure”).

5.2.2.9. Shearing stress – tangential force applied to the skin (also referred to as 

“lateral pressure”).

5.2.2.10. Torque – rotational force applied to the skin.

5.2.2.11. Residue factors – any factors related to the residue on the skin that can affect 

the recording of the skin (e.g., initial composition of the residue, distribution 

of residue on the skin, or redistribution of residue in an impression due to 

skin moving on a surface).

5.2.2.12. Surface conditions – any factors related to the surface that affect the 

recording of the skin (e.g., texture, curvature, pliability, or contaminants).

5.2.2.13. Environmental factors – any factors related to the environment (e.g., 

temperature, humidity, UV exposure, or time) that affect the appearance of 

the features after the impression is recorded on a surface.

5.2.2.14. Post-deposition factors – any non-environmental factors that affect an 

impression (e.g., overlays with other impressions or smearing caused by an 

object touching an impression).

5.2.2.15. Processing technique – method used to develop the features of a latent 

impression; each method has a signature appearance that can vary, typically 

because of residue issues or surface conditions.
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5.2.2.16. Recovery method – manner in which an impression is preserved (e.g., lift 

or photograph) that causes distortion (e.g., crease in tape, lens distortion, 

poor lighting, poor focus, low resolution).

5.2.2.17. Electronic capture error – inaccurate recording of a feature by an automated 

device (e.g., livescan stitching error, image acquisition or processing 

fidelity).

5.2.2.18. Atypical anatomy – any deviation from the typical range of shape, size, or 

proportions of the human hand or foot or any disruption in the formation 

of the skin driven by genetic or epigenetic factors (e.g., syndactyly or 

congenital ridge aplasia). Atypical anatomy does not cause issues related 

to biological stability or recordability of the features; however, if it is not 

recognized during analysis, it can cause an examiner to underestimate or 

overestimate the source diagnosticity or search diagnosticity of a given 

feature set.
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6. Appendix A: Ridges

Figure 1 – Examples of ridges in the distal phalanges of the hand.

Ridge Attributes

Attribute Example

Ridge Width (a)

Furrow Width (b)

Length

• Full Length (c)

• Partial Length (d)

Spacing (e)

Curvature (f and g)

Edge Shape

• Generally Straight (h)

• Protrusion (i)

• Intrusion (j)

Pore Position

• Pore to edge of ridge (k)

• Pore to Pore (l)

Figure 2 – Distal phalange photographed touching glass.

Open Field

Figure 3 –The corresponding open field is noted in the white box.

Table 1 – Examples of attributes of ridges.
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7. Appendix B: Minutiae

Minutiae Attributes

Attribute Example

Number

Density

Figure 4 –The image on the left has more minutiae and higher minutiae density than 

the image on the right. 

Orientation

Pattern Force 

Minutiae

Counter pattern 

Force Minutiae

Figure 5 - Pattern force minutiae sharing orientation in the outflow of a right loop on a 

distal phalange.

Figure 6 - Pattern force minutiae (orange and blue) and counter pattern force minutiae 

(red) in palm impressions.
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Figure 7 - Minutiae (non-pattern force) in a distal phalange of a hand above the core of 

a left loop.

Connectedness

• Ending 

Ridge 

• Bifurcation 

• Ambiguous 

Figure 8 – Ending ridges (green), bifurcations (blue), and ambiguous minutiae (red) in 

a distal phalange.

Compound 

Minutiae

See Table 3

Table 2 – Examples of attributes of minutiae.
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Compound Minutia Types

Minutia Type Definition Example

Short Ridge An independent ridge (defined by two ending 

ridges) with a length that is less than ten times 

the average width of the ridge.

Figure 9 – Short ridge

Dot An independent ridge with a length that is less 

than two times the average width of the ridge.

Figure 10 – Dot

Break A site along the ridge where the course of the 

ridge is interrupted, like a sink hole in the 

ridge. This length of the discontinuity is at 

least the width of the ridge, but no longer than 

twice the width of the ridge.

Figure 11 – Break

Enclosure A minutia defined by the merger of both ends 

of a short ridge with a neighboring ridge 

(defined by two bifurcations directed toward 

each other). The distance between the

bifurcations is less than ten times the average 

width of the ridges. Figure 12 – Enclosure

Overlap Where two ridges meet and overlap. The 

length of overlap is less than ten times the 

average width of the ridges.

Figure 13 – Overlap

Spur A minutia defined by the merger of one end of 

a short ridge with a neighboring ridge (defined 

by one bifurcation and one ending ridge). The 

distance between the ending ridge and 

bifurcation is less than ten times the average 

width of the ridges. Figure 14 – Spur

Crossbar A ridge that alters its course to zig-zag around 

other minutiae, similar to a train switching 

tracks. The transfer zone is less than ten times 

the average width of the ridges.
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Figure 15 – Crossbar

Bridge A minutia defined by the merger of a short 

ridge with two neighboring ridges. The path of 

the bridge tends not to be parallel to the 

neighboring ridges and the length of the bridge 

is no longer than five times the average width 

of the ridges. Figure 16 – Bridge

Opposing 

Bifurcations

A minutia defined by two bifurcations directed 

away from each other. The distance between 

the two bifurcations is less than five times the 

average width of the ridges.

Figure 17 – Opposing 

Bifurcations

Dock A minutia defined by an overlapping cluster of 

three ridge endings where the center ridge 

ending is in the opposite direction of the other 

two ridge endings and the length of overlap on 

each side of the center ridge is less than ten 

times the average width of the ridges. Figure 18 – Dock

Ending Ridge + 

Bifurcation 

Combination

A minutia defined by the end of a ridge leading 

to a bifurcation. The distance between the end 

of the ridge and the bifurcation is less than five 

times the average width of the ridges.

Figure 19 – Ending Ridge 

plus Bifurcation

Trifurcation/Double 

Bifurcation

A minutia defined by the merger of three 

ridges into one. This minutia type can appear 

as a trifurcation when the three ridges emanate 

from a common vertex or a double bifurcation 

when one ridge is not centered on a vertex with 

the other two ridges. The merger of the three 

ridges is contained within a distance less than 

three times the average width of the ridges.

Figure 20 – Trifurcation / 

Double Bifurcation

Return The location along an independent ridge where 

the ridge makes a 180oturn and the return is 

not part of a recurve associated with a tented 

arch, loop or whorl pattern.

Figure 21 – Return
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Merge Point The merger of the legs of two bifurcations into 

one ridge. The mergers (the points of the “M”) 

are contained within a distance less than five 

times the average width of the ridges.

Figure 22 – Merge Point

Table 3 – Examples of compound minutiae.
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8. Appendix C: Incipient Ridges

Figure 23 – Mature ridges and incipient ridges (selected incipient ridges are noted with black 

arrows and mature ridges are noted with blue arrows).

Incipient Ridge Attributes

Attribute Example

Number

Density

Figure 24 – The distal phalange on the left has fewer incipient ridges and lower incipient 

ridge density than the distal phalange on the right.
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Width (a)

Length (b)

Inter-Incipient 

Gap (c)

Edge Shapes

• Generally 

Straight

(d)

• Protrusio

n (e)

• Intrusion

(f)

Direction (g)

Figure 25 – Distal phalange photographed touching glass.

Table 4 – Examples of attributes of incipient ridges
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9. Appendix D: Dissociated Ridges

Dissociated Ridge Attributes

Attribute Example

Number

Density

 

Figure 26 – Impressions displaying dissociated ridges. The impression on the left has 

fewer dissociated ridges and a lower density of dissociated ridges (within the surface 

area of the rolled impressions) compared to the impression on the right.

Ridge Width (a)

Furrow Width (b)

Length (c)

Spacing (d)

Direction (e)

Curvature (f)

Figure 27 –Impression of a distal phalange displaying dissociated ridges.
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Edge Shape

• Generally 

Straight

(g)

• Protrusion

(h)

• Intrusion

(i)

Pore Position

• Pore to 

edge of 

ridge (j)

• Pore to 

Pore (k)

Figure 28 – Impression of a distal phalange displaying dissociated ridges.

Connectedness See connectedness examples under Minutiae

Table 5 – Examples of attributes of dissociated ridges
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10.Appendix E: Ridge Flows

Examples of Ridge Flows

Examples Examples

Figure 29 – Tented arch pattern from a distal phalange. Figure 30 – Thenar area of the palm.

Figure 31 – Hypothenar of a right palm. Figure 32 – Medial phalange.

Table 6 – Examples of ridge flows. 

Ridge Flow Attributes

Attribute Example

Divergence (a)

Convergence (b)

Curvature (c)

Figure 33 – Palm interdigital displaying ridge flow attributes.

Table 7 – Examples of attributes of ridge flow.
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11.Appendix F: Pattern Elements – Recurves and Triradii

Examples Examples

Figure 34 – Palm interdigital with one recurve and two 

triradii.

Figure 35 – Distal phalange with one recurve and one 

triradii.

Table 8 – Examples of recurves and triradii. 

Pattern Element Attributes

Attribute Example

Number

Figure 36 – Palm displaying two pattern elements (one recurve and one 

triradius).

Triradius Angle

Figure 37 – Three angles associated with a triradius.
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Recurve Ridge Count

Recurve Direction

Figure 38 – Recurves of a double loop whorl in a distal phalange displaying 

different recurve ridge counts and recurve directions.

Pattern Element 

Relationships

Figure 39 – Relationships (black lines) between recurves and triradii in a 

palm interdigital.

Table 9 – Examples of attributes of pattern elements
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12.Appendix G: Regular Creases

Figure 40 – Regular Creases of the Palm and Foot: DIC – Distal Interphalangeal Crease; PIC –

Proximal Interphalangeal Crease; PDC – Palmar Digital Crease/ Plantar Digital Crease; DTC –

Distal Transverse Crease; PTC – Proximal Transverse Crease; TC – Thenar Crease; WC – Wrist 

Crease.

Regular Crease Attributes

Attribute Example

Number
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Figure 41 – Palm with two palmar digital creases and a distal transverse crease.

Configuration

Figure 42 – Palmar digital crease configured as a single, braided crease and a double 

crease.

Spacing (a)

Width (b)

Length

• Partial 

(c)

Curvature (d)

Direction (e)

Position

Figure 43 – Attributes of regular creases. The positions of the creases in the hand are 

consistent with the distal transverse crease, proximal transverse crease and the thenar 

crease.

Edge Shapes

Figure 44 – Images of palms touching glass. Edge shapes of the distal transverse crease 

can be observed in the skin from both palms.
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Branching

Figure 45 – Pattern of branches of the distal transverse crease can be observed in the 

impression.

Table 10 – Examples of attributes of regular creases
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13.Appendix H: Irregular Creases and Wrinkles

Figure 46 – Irregular creases in the medial phalange of a finger (left) and the thenar region of a 

palm (right).

Irregular Crease and Wrinkle Attributes

Attribute Example

Number

Density

Figure 47 – A right palm impression on the left has a fewer irregular creases and wrinkles 

and lower density of irregular creases and wrinkles than the impression on the right.
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Width (a)

Spacing (b)

Length (c)

Curvature (d)

Direction (e)

Angle of 

Intersection (f)

Branching (g)

Figure 48 – Distal phalange with labeled wrinkle attributes.

Figure 49 – Thenar area labeled irregular creases attributes.

Table 11 – Examples of attributes of irregular creases and wrinkles.
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14.Appendix I: Scars

Figure 50 – Examples of scars from inked impressions.

Scar Attributes

Attribute Example

Width (a)

Length (b)

Surface Area

Curvature (c)

Direction (d)

Created 

Minutiae (e)

Edge Shapes (f)

Figure 51 – Distal phalanges that present scarring. 

Table 12 – Examples of attributes of scars.
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15.Appendix J: Unstable Features

Figure 52 – Examples of unstable features.

Unstable Feature Attributes

Attribute Example

Number

Figure 53 – Palm interdigital with two calluses.

Width (a)

Length (b)

Surface Area

Curvature (c)

Direction (d)

Edge Shapes (e)

Figure 54 – Attributes of the unstable feature (warts) are labeled; note the 

surface area would require a complex calculation.

Table 13 – Examples of attributes of unstable features.
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16.Appendix K: Shape of Impression

Figure 55 – Different areas of the palm touching glass.
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Shape Attributes

Attribute Example

Surface Area

Figure 56 – The surface area of the distal phalange (left) is significantly less 

than the surface area of a right palm hypothenar (right).

Outline

Figure 57 – There are natural borders caused by the hand and unnatural 

borders caused by the cropping of the image. The natural outer borders are 

traced in black. 

Table 14 – Examples of attributes of shape of an impression.
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17.Appendix L: Feature Sets and Relationships – Search 

Diagnosticity and Source Diagnosticity

Image Discussion

Figure 58 – Impression from a left 

palm.

The shape, ridge flow and triradius indicate palm. There is what appears 

to be a large crease dissecting the ridge flow. This could be the distal 

transverse crease based on its width and pattern of branching. The 

triradius angles are most consistent with the triradius under the index 

finger. 

Using the triradius as an anchor point, the triradii of all palms must be 

sufficiently recorded to support an exclusion. If the triradii are poorly 

recorded or failed to record in the exemplars, the broader ridge flow (to 

the left of the triradius as positioned) and its proximity to the triradius 

may provide enough support for exclusion if the exemplars appear to 

have areas near the triradii adequately recorded. Subsets of the feature 

set in the impression are adequate to support an identification (i.e., the 

entire area represented in the impression does not need to be recorded in 

the exemplar print).

Figure 59 – Impression of a proximal, 

medial and partial distal phalange.

Shape, regular creases, irregular creases, ridge flows and pattern 

elements indicate distal, medial, and proximal phalanges of a finger

with orientation shown. All three segments of the finger contain ridge 

detail; however, the distal phalange area is not adequately present. 

A standard fingerprint card does not provide fully rolled medial and 

proximal phalanges. Additional sufficiently recorded lower phalanges 

of all fingers (thumbs not required as the presence of three segments 

eliminates the thumbs as donor regions) are required to conduct 

comparisons. Subsets of the feature set in the impression are adequate to 

support an identification (i.e., the entire area represented in the 

impression does not need to be recorded in the exemplar print).

Table 15 – Examples of feature sets and search and source diagnosticity
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18.Appendix M: Quick Reference Summary Table

Attributes Search Diagnosticity Source Diagnosticity

Ridges ▪ Number

▪ Ridge Width

▪ Furrow Width

▪ Length 

▪ Spacing 

▪ Direction 

▪ Curvature 

▪ Edge Shapes 

▪ Pore Position 

▪ Open Field 

Low ▪ In general: surface area increases, source 

diagnosticity increases

▪ In general: open field increases in size, 

source diagnosticity of the open field 

increases

Minutiae ▪ Number

▪ Density

▪ Orientation 

▪ Connectedness 

▪ Compound Minutiae 

▪ Pattern Force Minutiae

▪ Counter Pattern Force 

Minutiae

Cluster of minutiae in a pattern force area 

generally increases search diagnosticity

Cluster of minutiae in a non-pattern force area 

generally decreases search diagnosticity

▪ In general: number increases, source 

diagnosticity increases

▪ Minutiae in a pattern force area can decrease 

source diagnosticity

▪ For a given cluster: depends on anatomical 

region, density of the minutiae, orientation

of the minutiae, distance between the 

minutiae, population of donors under 

consideration

Incipient Ridges ▪ Number

▪ Density

▪ Width

▪ Length

▪ Direction

▪ Inter-Incipient Gap

▪ Edge Shapes

Low ▪ In general: number increases, source 

diagnosticity increases

Dissociated Ridges ▪ Number 

▪ Density

▪ Ridge Width

▪ Furrow Width

Low ▪ In general: number increases, source 

diagnosticity increases
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Attributes Search Diagnosticity Source Diagnosticity

▪ Length

▪ Spacing

▪ Direction

▪ Curvature

▪ Edge Shapes

▪ Pore Position

▪ Connectedness

Ridge Flows ▪ Curvature

▪ Convergence

▪ Divergence

High, elevated in combination with additional 

features (e.g., shape or regular creases)

▪ Low

Pattern Elements: Recurves 

and Triradii

▪ Number

▪ Triradius Angle

▪ Recurve Ridge Count

▪ Pattern Element 

Relationships

▪ Recurve Direction

High ▪ Low

▪ Value depends on the region of skin

Regular Creases ▪ Number

▪ Configuration

▪ Spacing

▪ Position

▪ Width

▪ Length

▪ Curvature

▪ Direction

▪ Edge shapes

▪ Branching

High ▪ Low (number, configuration, position)

▪ Low to moderate (width, length, curvature, 

direction)

▪ Moderate to high (edge shapes, branching)

Irregular Creases ▪ Number

▪ Density

▪ Width

▪ Length

▪ Curvature

▪ Direction

▪ Branching

▪ Angle of intersection

▪ Spacing

▪ Higher in palm thenars, proximal and medial 

phalanges of the fingers, arches of the feet

▪ Lower in other regions of skin

▪ Lower in palm thenars, proximal and medial 

phalanges of the fingers, arches of the feet

▪ Higher in other regions of skin

▪ Branching and angles of intersections 

moderate to high

Wrinkles ▪ Number Low ▪ More wrinkles, higher source diagnosticity
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Attributes Search Diagnosticity Source Diagnosticity

▪ Density

▪ Width

▪ Length

▪ Curvature

▪ Direction

▪ Branching

▪ Angles of intersection

▪ Spacing

Scars ▪ Number

▪ Width

▪ Length

▪ Surface Area

▪ Curvature

▪ Direction

▪ Created Minutiae

▪ Edge shapes

Low ▪ The more complex and frequent, the higher 

the source diagnosticity

Unstable Features ▪ Number

▪ Width

▪ Length

▪ Surface Area

▪ Curvature

▪ Direction

▪ Edge shapes

Low ▪ The more complex and frequent, the higher 

the source diagnosticity

Shape of the Impression ▪ Surface area

▪ Outline

▪ Non-Ridged Skin Border

High Low

Table 16 – Quick Reference Summary Table
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19.Appendix N: References

19.1. Interpol. Part 2: Detailing the Method Using Common Terminology and Through the 

Definition and Application of Shared Principles. Interpol European Expert Group on 

Fingerprint Identification II – IEEGF II 2004

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Skin Impressions, Second Edition. CRC Press: New York, 2016. 

19.3. White, A. Features of the Friction Ridge Skin: Attributes, Diagnosticity, and 

Limitations. Journal of Forensic Identification 2022 72(1) 33-127.

19.4. Gibb, C. and White, A. Examination of Friction Ridge Impressions. In Max M. 

Houck (ed.) Encyclopedia of Forensic Sciences, Third Edition, vol. 2, pp. 316-327 

Oxford: Elsevier 2023

19.5. White, A. Distribution of Friction Ridge Patterns. In Max M. Houck (ed.) 

Encyclopedia of Forensic Sciences, Third Edition, vol. 2, pp. 48-70 Oxford: Elsevier 

2023

19.6. White, A. Biology of Friction Ridge Skin. In Max M. Houck (ed.) Encyclopedia of 

Forensic Sciences, Third Edition, vol. 1, pp. 301-312 Oxford: Elsevier 2023

19.7. Gutiérrez, E.; Galera, V.; Martínez, J.M.; Alonso, C. Biological Variability of the 

minutiae in the Fingerprints of a Sample of the Spanish Population. Forensic Science 

International 2007 172, 98-105. DOI: 10.1016/j.forsciint.2006.12.013

19.8. Gutiérrez-Redomero, E.; Alonso-Rodríguez, C.; Hernández-Hurtado, L.; RodríguezVillalba, J. Distribution of the Minutiae in the Fingerprints of a Sample of the Spanish 

Population. Forensic Science International 2011 208, 79-90. DOI: 

10.1016/j.forsciint.2010.11.006

19.9. Kondeková, M.; Benus R.; Masnicová, S.; Svábová, P. Distribution of Minutiae in 

Hypothenar Palm Prints in Slovak Adults: Indication for Personal Identification. 

Journal of Forensic Science 2020 65(4), 1303-1309. DOI 10.111/1556-40299

19.10. Okajima, M. Dermal and Epidermal Structures of the Volar Skin. Birth Defects: 

Original Article Series 1979 XV (6), 179-198.

19.11. Stücker, M.; Geil, M.; Kyeck, S.; Hoffman, K.; Röchling, A.; Memmel, U.; Altmeyer, 

P. Interpapillary Lines – The Variable Part of the Fingerprint. Journal of Forensic 

Science 2001 46 (4), 857-861.

19.12. Shaumann, B.; Alter, M. Dermatoglyphics in Medical Disorders. Springer-Verlag: 

New York 1976.

19.13. Maceo, A.; Carter, M.; Stromback, B. Palm Prints. In Siegel, J.; Saukko, P., Eds. 

Encyclopedia of Forensic Sciences, Second Edition, vol. 4, 29 – 36, Academic Press 

2013.

19.14. Fox, K.; Plato, C. Toe and Plantar Dermatoglyphics in Adult American Caucasians. 

American Journal of Physical Anthropology 1987 74 (1), 55-64.

19.15. Holt, S. The Genetics of Dermal Ridges. Charles Thomas Publisher: Illinois, 1968.

19.16. Kimura, S.; Kitagawa, T. Embryological Development of Human Palmer, Plantar, 

and Digital Flexion Creases. The Anatomical Record 1986 216 (2), 191-197.

19.17. Kimura, S.; Schaumann, B.; Shiota, K. Comparative Investigations of Human and Rat 

Dermatoglyphics: Palmar, Plantar and Digital Pads and Flexion Creases. Anatomical 

Science International 2002 77 (1), 34-46.
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19.18. Schmidt, H-M. and Lanz, U. Surgical Anatomy of the Hand. Thieme, New York 

2004.

19.19. Maceo, A. Anatomy and Physiology of Adult Friction Ridge Skin. In The Fingerprint 

Sourcebook; National Institute of Justice: Washington, D.C., p. 2-1 – 2-26, 2011.

19.20. Schreel, M.; Stonehouse, A.; Torres, A. Assessment of Friction Ridge Skin and Scars 

with a Focus on Latent Print Examination. Journal of Forensic Identification 2018

68(1), p. 43 – 75

19.21. Cicchetti, M. The Frequency of Scarred Friction Skin and the Classification of 

Characteristics Used to Recognize Scar Features. Journal of Forensic Identification

2022 72(4), p. 445 – 461

19.22. Drahansky, M.; Dolezel, M.; Urbanek, J.; Brezinova, E.; Kim, T. Influence of Skin 

Diseases on Fingerprint Recognition. Journal of Biomedicine and Biotechnology

2012, 626148. DOI: 10.1155/2012/626148.

19.23. Babler, W. Embryological Development of Epidermal Ridges and Their 

Configurations. Birth Defects Original Article Series 1991 27 (2), p. 95-112.

19.24. Neumann, C.; Champod, C.; Yoo, M.; Genessay, T. Quantifying the Weight of 

Fingerprint Evidence through the Spatial Relationship, Directions, and Types of 

Minutiae Observed on Fingermarks. Forensic Science International 2015 248, 154-

171. DOI: 10.1016/j.forsciint.2015.01.007

19.25. Lin, C.H.; Liu, J.; Osterburg, J.; Nicol, J. Fingerprint Comparison I: Similarity of 

Fingerprints. Journal of Forensic Science 1982 27 (2), 290-304.

19.26. Tao, X.; Chen, X.; Yang, X; Tian, J. Fingerprint Recognition with Identical Twin 

Fingerprints. PLoS ONE 2021 7 (4), e35704. DOI: 10.1371/journal.pone0035704.

19.27. Rivaldéria, N. and Gutiérrez-Redomero, E. Distribution of the minutiae in palm 

prints: Topological and sexual variability. Journal of Forensic Science 2020 66(1), p. 

135-148. DOI: 10.111/1556-4029.14583.

19.28. Park, J.; Shin, D.; Jung, W.; Chung, M. Improved Analysis of Palm Creases. 

Anatomy and Cell Biology 43(2), p. 169-177 2010. DOI: 10.5115/acd.2010.43.2.169

19.29. Sharma, D.K. and Sharma, V. Prevalence of Simian, Sydney and Suwon Creases and 

Their Association with Each Other, Body Sites, Handedness, Sex and 

Anomalies/Diseases/Syndromes in a Population of Central India. International 

Journal of Morphology 2011 29(3) p. 1069-1075

19.30. Kong, A.; Zhang, D.; Lu, G. A Study of Identical Twins’ Palmprints for Personal 

Identification. Pattern Recognition 2016 39 (11) 2149-2156. DOI: 

10.1016/j.patcog.2006.04.035.

19.31. Pandey, A.; Sharma, A. Formulation of Longitudinal Flexion Creases: Validation of 

Inheritance, Twin Diagnosis and Ethnic Variation. International Journal of Science 

and Research 2016 5 (4) p. 2296-2300.

19.32. Pandey, A.; Sharma, A. Formulation of Transverse Flexion Creases: Validation of 

Inheritance, Twin Diagnosis and Ethnic Variation. Journal of Humanities and Social 

Science 2016 21 (5), p. 41-49.

19.33. Cotney, J.; Leng, J.; Yin, J. Reilly, S.; DeMare, L.; Emera, D.; Ayoub, A.; Rakic, P.; 

Noonan, J. The Evolution of Lineage-Specific Regulatory Activities in the Human 

Embryonic Limb. Cell 2013 154(1) p. 185-196 DOI: 10.1016/j.cell.2013.05.056

19.34. Wolpert, L. Arms and the Man: The Problem of Symmetrical growth. PloS Biology

2010 8(9), e1000477
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19.35. Ray, E.. Frequency of Patterns in Palms. Journal of Forensic Identification 2012 . 62. 

568-587. 

19.36. Chapman, W.J., et al; “Markup Instructions for Extended Friction Ridge Features”; 

NIST Special Publication 1151, January 2013. 

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19.37. Annex F: Extended Feature Set Detailed Instructions, in American National Standard 

for Information Systems; “Data Format for the Interchange of Extended Friction 

Ridge Features”; ANSI/NIST-ITL 1-2011 (Update:2015), NIST Special Publication 

500-290 Edition 3 (2015).

20.Appendix O: Change Log

Version Date Change

1.0 09/2023 Original Issue