Chapter 14: FINGERPRINTS

FUNDAMENTALS OF FINGERPRINTS FIRST PRINCIPLE: Fingerprints are an Individual Characteristic. No two fingers have yet been found to possess identical ridge characteristics.

FUNDAMENTALS OF FINGERPRINTS MINUTIAE - Ridge Characteristics Define Individuality Assess: IDENTITY or Type of minutiae NUMBER of minutiae RELATIVE LOCATION of minutiae COMPARE POINT BY POINT POSSIBLY 150 POINTS ON THE AVERAGE FINGERPRINT

First Principle (cont) Ridge Characteristics

First Principle (cont)

FUNDAMENTALS OF FINGERPRINTS MINUTIAE - Ridge Characteristics Define Individuality HOW MANY POINTS MAKE A MATCH? Depends on experience and knowledge of the examiner Usually 8 to 16

First Principle (cont) The GBI requires 10-12 ridge characteristics for a match. The FBI will often take 7-10 characteristics for a match.

FUNDAMENTALS OF FINGERPRINTS SECOND PRINCIPLE: A Fingerprint will remain LARGELY UNCHANGED during an Individual’s Lifetime

Second Principle:

Second Principle (cont) Though efforts have been made to obscure one’s fingerprints, it would be totally impossible to obliterate all the ridge characteristics on the hand, and the presence of permanent scars only provides new characteristics of identification.

Second Principle (cont) John Dillinger, a notorious gangster, tried to destroy his own fingerprints by applying acid.

FUNDAMENTALS OF FINGERPRINTS THIRD PRINCIPLE: Fingerprints have general ridge patterns that permit them to be systematically classified. All fingerprints are divided into three classes on the basis of their general pattern: Loops, Whorls, and Arches

Third Principle Terminology Type Lines - two diverging ridges usually coming into and splitting around an obstruction (delta) Delta – a triangular area where the ridges radiate outward in three directions. Core – approximate center of the pattern Core

What are the three ways to classify fingerprints?

FUNDAMENTALS OF FINGERPRINTS ARCHES 5% LOOPS 60% - 65% WHORLS 30% - 35%

FUNDAMENTALS OF FINGERPRINTS ARCHES - least common of three patterns RIDGES ENTER ONE SIDE OF PATTERN AND EXIT ANOTHER Arches do not have type lines, deltas, or cores. 2 Types PLAIN ARCHES - wavelike pattern TENTED ARCHES - sharp spike

Third Principle – Plain Arch A plain arch is that type of pattern in which the ridges enter upon one side, make a rise or wave in the center and flow or tend to flow out upon the opposite side.

Third Principle – Tented Arch A tented arch is that type of pattern which possesses either an angle, an upthrust, or two of the three basic characteristics of a loop.

FUNDAMENTALS OF FINGERPRINTS LOOPS - most common type Ridges enter one side and exit same side ULNAR LOOP - opens toward little finger RADIAL LOOP - opens toward thumb Must identify on which hand the print is found

FUNDAMENTALS OF FINGERPRINTS LOOPS - CORE TYPE LINES DELTA

FUNDAMENTALS OF FINGERPRINTS WHORLS – FOUR types TYPES Plain Central pocket Double loop Accidental ALL HAVE TYPE LINES, A CORE & and at least TWO DELTAS

Third Principle – Plain Whorl Plain whorl consists of one or more ridges which make or tend to make a complete circuit, with two deltas, between which an imaginary line is drawn.

Third Principle - Central Pocket Whorl Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

Third Principle – Double Loop Whorl Double loop whorl consists of two separate loop formations, with two separate and distinct sets of shoulders and two deltas.

Third Principle – Accidental Whorl Accidental whorls consist of a combination of two different types of patterns with the exception of the plain arch, or a pattern which conforms to none of the definitions. Accidental whorls will have two or more deltas.

Classification The original Henry system converted ridge patterns on all 10 fingers into a series of letters and numbers arranged in the form of a fraction. The FBI needed to expand Henry’s classification capacity by modifying and adding additional extensions due to the increasing number of prints on file. This modification is known as the FBI system.

Classification (cont) The Primary Classification is the first step in the FBI system. The steps for classification are: Make a print of each finger A value of zero is given to any print that is an arch or loop. A number is given to any print that is a whorl, starting with 16 for the first pair, 8 for the second, 4, 2 and a value of 1 for the last pair.

Classification (cont) The values are placed in a fraction sequence. 1/1 is added to the fraction total. The final number is the primary classification number.

Primary Classification The Henry—FBI Classification Each finger is given a point value right left

Henry’s Finger Numbers and Finger Values L Pinky L Ring L Middle L Index L Thumb R Thumb R Index R Middle R Ring R Pinky Finger Number 10 9 8 7 6 1 2 3 4 5 Value (if Whorl) 16 Primary grouping determined by claculating the ratio of one plus the sum of the values of the whorl-patterned, even numbered fingers divided by one plus the sum of the whorl-patterned, odd numbered fingers. 1 + (Sum of whorled, EVEN finger values) = Primary Grouping Ratio 1 + (Sum of whorled , ODD finger values)

Primary Classification An example sequence: 0 + 8 + 0 + 0 + 0 + 1 = 9 16 + 0 + 0 + 0 +0 + 1 17 About 25% of the population have a 1/1primary classification, meaning they have only arches or loops, or combination of both. right left

Fingerprint Comparison Three types of fingerprint files are in use: Manual System — An examiner thumbs through each fingerprint card on file and makes an identification with no predetermined minimum set of comparison points. The Semi automated System — IBM punch cards are used and compared to similar cards, according to Henry’s system. Fully Automated (AFIS) — a computerized system that houses a large data base of fingerprints of previously arrested persons.

Automated Fingerprint Identification System (AFIS) uses automatic scanning devices that convert the image of a fingerprint into digital minutiae that contain data showing ridge endings and bifurcations. When the scan is complete, the computer produces a list of file prints with the closest correlation to the search print. The selected prints are examined by an expert; AFIS makes no final decision.