FINGERPRINT CAPTURE AND PATTERN AREA DETERMINATION

Forensic Biometric Identification Solutions LLC.

Small sample of Module 3

COMMON FINGERPRINT TERMSUSED IN THIS TRAINING PROGRAM

Bifurcation, is the forking or dividing of one ridge into two or more ridges.

Divergence, is the spreading apart of two ridges that have been running parallel or nearly parallel.

Fingerprint patterns fall into 3 major pattern groups loops, arches and whorls. Each grouping has the same general characteristics.

Pattern area is the part of the finger impression used in the interpretation and classification of a finger.

Type lines may be defined as the two innermost ridges that surround or tend to surround the pattern area.

Focal points are found within most pattern area’s usually a delta and core.

The delta first obstruction at the point of divergence of the type lines in front of or nearest the center of the divergence.

Core approximate center of the patter area.

Tracings are used to break down whorl patterns into smaller sub-groupings.

Automated fingerprint identifications systems ( AFIS ) are fingerprint search systems designed to search, store and retrieve fingerprint cards.

Line of Flow imaginary line between the delta and core in loop and whorl patterns. Line of flow is used to determine sufficient recurve in patterns.

horizontal plane is the ridge directly below an up thrusting or angular ridge in a tented arch pattern, the baseline ridge enters the pattern may rise slightly and exits on the opposite side from which it entered.

PERMANENT & UNIQUE TO AN INDIVIDUALFingerprints have been used as a means of identifications for more than 2000

years. In 1890 the first textbook published on fingerprints by Sir Francis Galton argued no

two fingerprints are the same, and that fingerprints remain unchanged over time.

Today, the American Institute of Applied Science states “ The basis of fingerprint

identification is the premise that the configurations formed by the raised ridges of the palmar

surface of the hands are unique and do not undergo any natural changes, except growth, from

fetal life until decomposition”. The permanence and uniqueness of fingerprint ridge detail

is an accepted fact in the scientific community as often demonstrated in terminology

used by scientists; a chemist for example will often use the term "fingerprint region" to

describe an area of a chemical that can be used to identify it. In addition to the scientific

principles of the permanence and uniqueness of fingerprint ridge detail, it was found that

based on the variations in the patterns formed by the ridges, the fingerprints could be

grouped into a small number of pattern types. This ability to classify fingerprint pattern type has

allowed fingerprints to replace previous Identification systems , today fingerprints

account for more positive Identifications of individuals worldwide daily, than any other human

identification procedure.

UTILIZING FINGERPRINTS

Classification systems were developed to utilize the distinctive ridges that appear on the

inside of the end joints of the fingers and thumbs. Fingerprints fall into three major pattern

Groupings (loop, arch, whorl). Each pattern group has the same general characteristics or

family resemblance. The three major pattern types may be further divided into subgroups by

means of smaller differences existing between the patterns, in the same major group. The

arch group includes the plain arch and the tented arch the loop group includes the radial and

ulnar loops. The whorl group includes four types of whorl, the plain whorl, central pocket

Loop whorl , double loop whorl, and accidental whorl. This ability to categorize each finger

allowed agencies to store the fingerprint cards in small easy to mange bins of fingerprint cards

allowing quick and accurate access to the fingerprint database. The Henry classification

utilized both the major pattern grouping and the pattern subgroups in it’s classification

formula which allowed agencies to store, search and retrieve fingerprint records quickly and

accurately. The systems could be used by small agencies with hundreds of fingerprint cards

as well as large state agencies housing millions of fingerprint records. In the early 90’s

automated fingerprint identification system began to replace the manual fingerprint systems.

The automated systems allowed classification rules to be relaxed utilizing computer

technology to store, search and retrieve fingerprint records based more on minutiae detail

than pattern type.

Fingerprint Patterns

All fingerprint images can be categorized into one of these three(3) main pattern groupings. These pattern groupings are defined by their unique general characteristics. The patterns groupings can be further divided into sub-groups by means of smaller differences existing between the patterns in the same pattern group.In this course we will look at the main pattern grouping as well as the sub groups associated with them. There are a number of rules and definitions used in determining pattern and pattern area, which we will go over in the next few slides.

Loops Arches Whorls

Simple way to remember the major pattern groups LAW

DETERMINING MAJOR PATTERN GROUPING

In order to determine the pattern grouping for a fingerprint,

there are a number of guidelines followed in all classification

systems, these guidelines insure uniformity in fingerprint

pattern determination. The fingerprint pattern today is used as

a filter in automated fingerprint systems and a correct pattern

can impact the results of a latent or ten print search, The 1st.

area of interest in determining pattern type is the pattern area.

Pattern area is where you will find all the information required

to accurately determine the correct fingerprint pattern. The

pattern area contains the focal points used in determining

the fingerprint pattern. The pattern area is present in all

patterns, but in most arch patterns it is impossible to define.

The fingerprint pattern area in loops, whorls and some arch

patterns will contain the delta(s), core and ridges used in the

pattern determination process.

Automated Fingerprint Identification Systems when searching latent Images normally are 60-70 % accurate. Usingpattern to limit the numberof suspects increases thelikelihood of identifying alatent with a suspect in the database.

Red lines highlight type lines that define the pattern area. Pattern area is that part of a loop or whorl in which appear the core(s), delta(s), and ridge(s) with which we are concerned in fingerprint pattern determination and classification.

The Pattern Area is defined by the Typelines.The typelines are the two (2) innermost ridges that run parallel, diverge and surround or tend to surround an area of ridge detail. The enclosed area of ridge detail is defined as the pattern area.

TYPE LINES ARE NOT ALWAYS CONTINUOUS RIDGES

Type lines are not may not always two

continuous ridges, in fact most typelines

are not continuous ridges. The causes of the

breaks could be natural, damage to the

finger or just a poorly captured fingerprint

images. Most typelines will have slight ridge

breaks, bifurcating ridges or the ridge will

end abruptly. When there is a definite break

in a type line, the ridge immediately outside

of the break is considered the continuation

of the ridge. If the type line bifurcates, take

the ridge that tends toward the middle of the

pattern area as the continuation of the

type line.

DETERMINING PATTERN AREA

The small breaks in the ridge due to poor

image quality, worn ridges etc. are not considered definite ridge endings and

you continue following the ridge after the

slight break. As we stated earlier the pattern

area contains the cores, deltas, and ridges

which are required for accurate fingerprint

patter determination.

The break in this type line is caused by a temporary scar and is not considered a breakIn the type line.

Small break due to the way Prints were captured ignoreThe break

ANGLED RIDGES

Angled ridges cannot be used as type lines. The angled ridge is formed by two(2) ridges, one abutting up against the other ridge. The definition for a type line the two (2) innermost ridges that run parallel, diverge and surround or tend to surround an area of ridge detail. Since an angle is formed by formed by two separate and distinct ridges it does not meet the definition for a type line..

2 ridges meeting forming an angleCannot be used as a type line.

Type lines are these 2 innermostRidges that run parallel and diverge

TYPE LINES BIFURCATING RIDGES

In the example to the right we see B a bifurcation

one(1) ridge splitting into two (2) ridges. The

bifurcation does not run parallel to the type line

A, so it can’t be used as a type line. We move

outward to ridge which does run parallel to A, this

meets the criteria for a type line and is in fact the

Type line in this pattern.

Bifurcation 1 ridgeinto 2 ridges

Type lines, ridges run Parallel then diverge

ABC

TYPE LINES

Two forks of a bifurcation cannot be used as

type lines. The exception to this rule is when the

forks run parallel after bifurcating and then

diverge. In such a case the two forks become

the two innermost ridges required by the

definition.

The rule for a type line is it must run parallel, a type lines can be very short. Care must be exercised when locating the type line.

NOW THAT YOU HAVE DETERMINED PATTERN AREA

Once the pattern area has been determined,

you can locate theca points of that pattern:

Delta Core Ridge detail

First we’ll look at defining and determining

the delta of the fingerprint pattern.

Area’s where the delta formations are usually found. The first obstruction of any nature at the point of divergence of the type lines in front of or nearest the center of the divergence.

The delta is the first ridge or part of a ridge at or in front of and nearest the center of the point of divergence of the fingerprint type lines.

DELTA

The delta may be:

● A bifurcation

● An abrupt ending ridge

● A dot

● A short ridge

● A meeting of two ridges

● A point on the first recurving ridge located nearest to the center and in front of the divergence of the type lines.

CORE

Cores, as the name implies, the core is usually the

approximate center of the pattern area. In loop

patterns the rule used to determine the core is the

sufficient recurve rule. Simply stated there has to

be a recurving ridge with a sufficient recurve. A

sufficient recurving ridge in a looping pattern is one

free of appendages that abut on the outside of the

ridge at 90 degree angle between the shoulders of

the looping ridge. Since a majority of the patterns

are looping ridge types of patterns we will look at

determining the core in these patterns 1st.

SUFFICIENT RECURVE

In order to determine core placement in a looping fingerprint pattern, you first need To determine if the pattern has a

sufficient recurve. Sufficient recurve is defined as the innermost recurving ridge that enters the pattern area, recurves and exits or tends to exit on the same side as the ridge entered. The ridge must be free of Any ridge appendages abutting at rightangles on the outside of the recurve between the shoulders of the looping ridge.

SHOULDER

The shoulders on looping ridges are considered the point at which the ridges begin to

curve or turn inward.

Shoulder

Shoulder

Ridge area that must be free of anyridge appendages abutting at rightangles on the outside of theRecurve.

SUFFICIENT RECURVE

What do you do if the innermostlooping ridge is spoiled ?

Spoils the recurve look for a sufficient recurve in the nextinnermost looping ridge.

This does meet the requirement And is a sufficient recurve.

You move to the next recurve and determine if it has a good recurve. This process is followed until you get a good recurve or you are out of the pattern area.

INNERMOST SUFFICIENT RECURVE

Examples of the innermost recurving ridges being spoiled and dropping back to the next recurving ridge until you get a recurving ridge that is not spoiled. Once you have that you can determine the core placement.

Innermost sufficient recurve

Core

Innermost sufficient recurve

Core

Innermost sufficient recurve

Core

RIDGE COUNTING

The ridge count is the number of ridges intervening between the delta and the core. The ridge count is usually

determined utilizing a red line found on the reticule of the fingerprint glass. The line is lined up between the delta

and core is used count to insure accuracy. Ridges that touch or cross the line become your ridge count, in the event

there is a bifurcation of a ridge exactly at the point where the imaginary line would be drawn, two ridges are

counted. Fragments and dots are counted as ridges only if they appear to be as thick and heavy as the other ridges

In the immediate pattern. The delta and core are not counted. Ridge counting was used extensively in the Henry

classification formula with the advent of automated fingerprint identification systems (AFIS) ridge counting is

seldom used though a ridge count across a looping ridge is a required element of a loop pattern.

Delta

Core

Ridge 1

Ridge 2

Ridge 3

Ridge Count of 3

Quiz Correctly IdentifyType linesDeltaCore

Quiz Correctly IdentifyType linesDeltaCore

Delta

Core

Delta

Core

Delta

Core

Delta

Core