Fingerprints

Forensic Science

Latent Fingerprinting

Fingerprinting

Background

• The use of fingerprints as a means of identification is an ancient one.

• Dates back to the times of ancient Assyria and Babylon, where kings and aristocrats used their fingerprints to literally leave their mark as a sign of who they were.

• This was done because of a common belief that,“no two people had the same set of fingerprints”

Background

• Fingerprints have remained a valuable means of identification of an individual because:

1. they are totally unique to the individual

2. they never change (Immutability)

• Fingerprints are hereditary - they form before you are born. (by about 4 months)

• They never change and they are even around a short while after death.

THE HENRY-GALTON FINGERPRINT CLASSIFICATION

• There are three basic patterns in classifying fingerprints;

Arch

Loop

Whorl

THE HENRY-GALTON FINGERPRINT CLASSIFICATION

Fingerprints and a fingerprint classification schema involving six categories: (a) arch, (b) tented arch, (c) right loop, (d) left loop, (e) whorl, and (f) twin loop. Critical points in a fingerprint,called core and delta, are marked as squares and triangles.

Fingerprinting

• Every person has minute raised ridges of skin on the inside surfaces of their hands and fingers and on the bottom surfaces of their feet and toes, known as 'friction ridge skin'.

• The friction ridges provide a gripping surface - in much the same way that the tread pattern of a car tyre does.

• Friction ridges do not run evenly and unbroken across our fingers, hands, toes and feet. Rather, they display a number of characteristics known as minutiae.

FingerprintingThe principle categories of minutiae

are as follows:• ridge ending - a ridge that ends

abruptly; • bifurcation - a single ridge that

divides into two ridges;

Fingerprinting• lake or enclosure - a single ridge that

bifurcates and reunites shortly afterwards to continue as a single ridge;

• short ridge - a ridge that commences, travels a short distance and then ends;

Fingerprinting• dot - an independent ridge with

approximately equal length and width;

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

• crossover - a short ridge that runs between two parallel ridges.

Collecting Fingerprints

1. Dusting powder - Fine powder (usually carbon) is brushed onto a nonporous surface and sticks to the moisture left behind.

2. Iodine - fumes from heated iodine react with oils and turns purple after heating. This technique is used for porous surfaces such as

fabrics.3. Alternative light sources - Argon lasers,

Infrared and ultraviolet lamps can visualise prints without the use of chemicals.

4. Superglue fuming (cyanocrylate) - superglue is heated to fuming point and reacts with moisture to coat fingerprints with a film of plastic.