Fingerprints. Background Information Each fingerprint is made up of friction ridges, that do not change over time (unless scarring occurs) Fingerprints.

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Background Background InformationInformation

Each fingerprint is made up of friction ridges, that do not change over time (unless scarring occurs)

Fingerprints are formed in the wombEach fingerprint is a deposit of wastes

when a person comes in contact with a surface

98 % is water & salts, 1% oils, 1% amino acids

Prints at a Crime Prints at a Crime SceneScene

Divided into 3 typesPatent PrintPlastic PrintLatent Print

Patent PrintPatent PrintCan be seen with the naked

eyeMade by a hand that had

blood, grease, oil, or any other sticky substance on it

Plastic PrintPlastic PrintVisible to the naked eyeFormed when an

impression is made in a soft substance such as putty, glue, dust, or butter

Latent PrintLatent PrintMost common typeCannot be seen without

applying powder or chemicalsSubstances adhere to the

amino acids or oils in the fingerprint and make it visible

Patterns of Patterns of FingerprintsFingerprints

3 basic types of patternsArch : 5% of populationLoop : 65% of populationWhorl : 30% of population

Basic FingerprintsBasic FingerprintsARCH LOOP WHORL

Plain Arch Left Radial Loop

Plain Whorl

Tented Arch Left Ulnar Loop Central Loop Whorl

Right Radial Loop

Double Loop Whorl

Right Ulnar Loop

Accidental Whorl

The ArchThe ArchFormed when the ridge lines

go from one side, rises in the middle, and leaves on the other side (like a wave)

Tented arches are more pointedNo ridgecount

Example of ArchExample of Arch

The LoopThe LoopRidge lines enters & exits on the

same side of the fingerType is determined by the

direction the ridges come & leavesIf it is from the thumb-side of the

finger, it is called a RADIAL LOOPIf it is from the little finger side it

is called an ULNAR LOOP

Examples of Examples of LoopsLoops

The DeltaThe DeltaWhorls are subdivided using a

ridge characteristic called a DELTA

DELTA: Triangle pattern (ridge forks & nearby ridge)

Whorls have 2 deltas, loops have 1 delta & arches have 0 deltas

The WhorlThe Whorl

Ridge Ridge CharacteristicsCharacteristics

BIFURCATION (or fork): ridge splits into 2 friction ridges

ENCLOSURE: forms an ovalENDING RIDGES: ridges

that stop abruptly

Ridge Ridge Characteristics Characteristics

ContinuedContinuedSHORT RIDGES: begin & end

abruptly, traveling a short distance

RIDGE DOT: isolated ridge that’s length is approximately its width

Examples of Ridge Examples of Ridge CharacteristicsCharacteristics

Identifying Identifying FingerprintsFingerprints

8-12 points of comparison must be in common to declare the 2 prints a match

When a partial print is available, as many characteristics must be matched as possible

Characteristics can be matched to the AFIS (Automated Fingerprint Identification System)

Example of Positive IDExample of Positive ID

Dusting fo r FI ngerpr ints

W O O D M E TA L P L A S TIC G L A S S TIL E

N O N P O R O U SS U R F A C E S

Chem ica l l y Fingerpr intingCyan oacryla te (Su p erglu e), I od in e, Nin h yd r in

P A P E R U N F IN IS H E D W O O D W A L L P A P E R

P O R O U S S U R F A C E S