Friction Ridge Identification

Created as a supplement to Chapter 15 of Fingerprint Identification By William Leo Copyright © 2004 All Rights Reserved

“Workers familiar with finger-print minutiae all affirm that there are no two duplicate prints of different fingers. They recognize many qualities other than the mere occurrences of details. The minutiae, like total patterns, have individuality. The interruption between two ridge ends may be short or long, the ridges may or may not deviate in direction as they terminate; bifurcations exhibit varying spreads, and many similar individual distinctions of minutiae occur. “Workers familiar with finger-print minutiae all affirm that there are no two duplicate prints of different fingers. They recognize many qualities other than the mere occurrences of details. The minutiae, like total patterns, have individuality. The interruption between two ridge ends may be short or long, the ridges may or may not deviate in direction as they terminate; bifurcations exhibit varying spreads, and many similar individual distinctions of minutiae occur.

When all these finer qualities are appreciated, it is not surprising that identifications of individuals are possible when only partial prints are available.” Finger Prints, Palms and Soles An Introduction to Dermatoglyphics Doctors Harold Cummins & Charles Midlo 1943, Pages 154 & 155

All areas of friction skin ( fingerprints, palms, and the toes and soles of the feet) are: All areas of friction skin ( fingerprints, palms, and the toes and soles of the feet) are: Permanent - Do not naturally change with time. Permanent - Do not naturally change with time. Unique - Therefore Allowing individualization Unique - Therefore Allowing individualization

Ridge Features and Clarity The level of clarity or quality of detail will determine the type of features available for comparison and the amount of detail needed to identify. The level of clarity or quality of detail will determine the type of features available for comparison and the amount of detail needed to identify. This is why there is not a pre- determine standard as to the amount of detail needed for an identification This is why there is not a pre- determine standard as to the amount of detail needed for an identification

Level 1 Detail Ridge Flow Ridge Flow Class characteristics only – No individualizing detail Class characteristics only – No individualizing detail Fingerprint patterns and ridge flow (shape) Fingerprint patterns and ridge flow (shape)

Level 2 Detail Individual Ridge Path Individual Ridge Path Major ridge features Major ridge features Ridge endings, bifurcations, etc, their positions and relationship to other features Ridge endings, bifurcations, etc, their positions and relationship to other features Allows individualization Allows individualization

Level 3 Detail Individual ridge Appearance Individual ridge Appearance Highest level of detail Highest level of detail Smallest features (pore & ridge structure) are visible for comparison. Smallest features (pore & ridge structure) are visible for comparison. The most individualizing detail The most individualizing detail

“A finger print is too complex a structure and its numerous details, definite as they are, are as arbitrary in their occurrence and arrangement as are the pebbles on the beach, no square foot of which could ever be duplicated by any other. It is always so with natural objects; the details are so numberless, and so independent of the rest, that there are no duplicates.” Personal Identification, Page Wilder PhD and Wentworth, 1918

The Identification Process The ACE/V Method The ACE/V Method Analysis Analysis Comparison Comparison Evaluation Evaluation Plus Plus Verification Verification

Analysis The print is examined to determine what detail is present and it’s quality (levels of clarity). The print is examined to determine what detail is present and it’s quality (levels of clarity). Does the print contain sufficient detail to be compared and identified? Does the print contain sufficient detail to be compared and identified? What area of friction skin may it have come from? What area of friction skin may it have come from?

Comparison The unknown print is orientated to the known exemplar. The unknown print is orientated to the known exemplar. A side by side comparison is made. A side by side comparison is made.

Possible Conclusions An identification (individualization) An identification (individualization) An elimination An elimination Inconclusive Inconclusive

Evaluation Is the detail (features) in agreement or in other words are they the same? Is the detail (features) in agreement or in other words are they the same? If so an identification is made. If so an identification is made. Is the detail (features) different? Is the detail (features) different? If so an elimination is made If so an elimination is made If there is insufficient detail to I.D. or eliminate, the comparison would be inconclusive If there is insufficient detail to I.D. or eliminate, the comparison would be inconclusive

Verification The ACE process is repeated by another examiner – independently The ACE process is repeated by another examiner – independently This is done as a quality control and to identify errors. This is done as a quality control and to identify errors. The fact that results can be repeated or duplicated independently demonstrates that fingerprint identification is not subjective. The fact that results can be repeated or duplicated independently demonstrates that fingerprint identification is not subjective.