What is your most precious piece of identification? Your social security card? A school I.D.? Your movie rental pass?

.....It may become your thumbprint…..!!!

Objective:Objective:

To learn the

ө Definitionө Principlesө Why fingerprinting?ө Types (or) patternsө visibilityө methods of visualizingө methods for collecting and preserving

impressionө AFIS- automated fingerprint identification

system

DEFINITION:

A fingerprint is an impression of the friction ridges on all parts of the finger.

FUNDAMENTAL PRINCIPLES OF FINGERPRINTS:

1) No Two Individual will have identical fingerprints. No two fingers have yet been found to possess identical ridge characteristics.

2) Fingerprints stay the same throughout our lives. A fingerprint is an individual characteristic. [Attempts at destroying pattern has failed]

3) Limited variety in patterns allows systematic classification of an in individuals fingerprints.

Why Fingerprint Identification?Why Fingerprint Identification?

Fingerprints offer an infallible means of personal identification. That is the essential explanation for their having supplanted other methods of establishing the identities of criminals reluctant to admit previous arrests.

The science of fingerprint Identification stands out among all other forensic sciences for many reasons,

Other visible human characteristics change - fingerprints do not.

Other Ridge Other Ridge Characteristics:Characteristics:

The principle categories of minutiae are as follows:

› ridge ending - a ridge that ends abruptly;

› bifurcation - a single ridge that divides into two ridges;

› short ridge, island or independent ridge - a ridge that commences, travels a short distance and then ends;

› dot - an independent ridge with approximately equal length and width;

› spur - a bifurcation with a short ridge branching off a longer ridge; and

› crossover or bridge - a short ridge that runs between two parallel ridges.

Patterns of fingerprints

Fingerprint PatternsFingerprint Patterns• Loops:

– Ridge lines enter from one side and curve around to exit from the same side

– 60-65% of population• Whorls:

– Rounded or circular ridge pattern– 30-35% of population

• Arches:– Ridge lines enter from one side of print and

exit out the other– 5% of population

LoopsLoops

• Ulnar loop- opens toward little finger• Radial loop- opens toward thumb• Type lines are two diverging ridges• At ridge point at or nearest divergence is delta• All loops must have one delta• Core is center of pattern

WhorlsWhorls

• Whorls are divided into four distinct groups.

• Plain, central pocket loop, double loop, accidental.

• they have type lines and minimum 2 deltas.

• Plain whorl & central pocket loop have at least one ridge.

• The ridge is of the form of spiral, oval or any variant of a circle.

ArchesArchesArches are divided into 2 distinct groups; plain & tented arches.

• Plain arch simplest & formed by ridges entering one side and exiting opposite side. Ridges rise in center of pattern and form wave-like patterns.

• Tented arch have at the center a sharp up thrust or spike instead of like a wave; arches don’t have type lines, deltas or cores

Fingerprint Fingerprint visibilityvisibility• Visible prints or patent

These are friction ridge impressions of unknown origins which are obvious to the human eye and are caused by a transfer of foreign material on the finger, onto a surface.In dried blood, paint, etc.

• Plastic prints A plastic print is a friction ridge impression from a finger or palm (or toe/foot) deposited in a material that retains the shape of the ridge detail.In moldable substance: gum, putty

• Latent printsAlthough the word latent means hidden or invisible, in modern usage for forensic science the term latent prints means any chance of accidental impression left by friction ridge skin on a surface, regardless of whether it is visible or invisible at the time of deposition.Not visible Must me visualized by chemical method Fingerprint types

Visualization of Latent Visualization of Latent Prints:Prints:

• On hard surfaces:– Powder

• Grey or black• Florescent• Magnetic

– Superglue

• On soft surfaces:– Iodine fuming

• Nonpermanent visualization

– Ninhydrin• Reacts with proteins

– AgNO3

• Reacts with salt

On hard surfaces:POWDERS:• Gray colored powder used surfaces like mirrors & metal surfaces they photograph black• Black powder : white or light-colored surfaces• Magnetic sensitive powders spread over surface with magnet form called Magna Brush; no bristles come in contact with surface so less chance print is damaged.• Fluorescent powders used to develop prints & fluoresce under UV light; photo taken of print under UV light avoid color surface obscure it.Dusting to visualize a latent print on finished leather & rough plastic is best done with a fiber glass brush.Camel hair brushes are also used.

SUPER GLUE FUMING : Latent print development on non-

porous surfaces like metals, electrical tape, leather, plastic bags. Cyanoacrylate ester chemical in super glue interacts and visualizes latent print.

Picture of latent fingerprint brush

• IODINE FUMING: – uses solid crystal. Examiner photos print immediately or use 1%

solution of starch in water & spray• Physical developer silver nitrate-based liquid reagent, effect on

former wet porous surfaces & undetectable using previous methods• One wishes to use all previous methods on same surface first fume

with iodine, NINHYDRIN, then physical developer.• These methods used on porous surfaces like paper, card board etc.• Print turns blue which may take several weeks to months.• Ninhydrin sprayed on porous surface (paper) & forms purple-blue

color with amino acids or protein present in trace amounts in perspiration .

• Prints begin to appear with in an hour or 2 but weaker prints take 24-48 hours; development hastened if heated in oven or hotplate.

On soft surfaces:On soft surfaces:

Preservation of Preservation of fingerprintsfingerprints

• Dusted prints are lifted on tape and placed on contrasting color card

• Chemically developed prints are photographed

AFISAFIS• Automated Fingerprint Identification system• Digitally encodes fingerprints by ridge ending and

bifurcations• Allows high-speed computer comparison• Software can subtract out background or enhance imageDigital imaging for fingerprint Digital imaging for fingerprint enhancementenhancement

• Digital imaging -process picture converted into digital file made up of pixels or electronic dots

• Digital imaging software help enhance fingerprints for more comprehensive & accurate analysis

• FFT or frequency Fourier transform used to identify periodic or repetitive patterns such as lines or dots that are interfering with the interpretation of the image

• Digital imaging does allow for simultaneous comparison of two prints

• After an investigator visualize print a 1:1 photo is taken

Digital imaging of Digital imaging of fingerprintsfingerprints