FINGERPRINTS

Chapter 14

Forensic Science

History of Fingerprinting

Bertillon (1883) First system for identification Galton (1892) Published first textbook: Finger

Prints Henry (1897) Fingerprint system adopted by

Scotland Yard NY City Civil Service Commission (1901) used

to certify all applications FBI (1924) combined prison records from

Leavenworth with their records to form the first national fingerprint “database”.

Three Fundamental Principles

Fingerprints show individual characteristics

Fingerprints do not change over a lifetime

Fingerprints have ridge patterns that can be easily classified

1st Principle: No two fingerprints look alike Classified by ridge

patterns or minutiae Ridge patterns must

match in both characteristics and location on the finger

No national standard but 8-16 ridge patterns are needed between a unknown and known fingerprint for there to be a match

2nd Principle: Fingerprints stay the same over a lifetime

Friction ridges found on lips, fingers and palms of hands and soles of feet

Outer layer of skin - epidermis Inner layer - dermis Junction between the two layers

is - dermal papillae John Dillinger tried to obliterate

his finger prints by making deep cuts and pouring sulfuric acid into the cuts. Within a few years the same friction ridge patterns returned with some scaring. Post Mortem fingerprints taken by the FBI confirmed that his prints were unchanged.

2nd Principle Raised lines or hills - Ridges

The valleys between the hills - Grooves

Pores in between the ridges are openings for sweat glands

Sweat and oils leave an impression on the surface - latent print

3rd Principle: Classified Ridge Patterns Three Ridge Classes:

LOOPS - 60 to 65%

WHORLS - 30 to 35%

ARCHES - 5%

Percentage of the patterns found on the epidermis in the general population

Classification

LOOPS

In order to distinguish between ulnar and radial loops you must: 1) know from which hand the loop pattern comes from 2) place

your hand palm side down over top of the impression and determine if the recurving ridges originate from the little finger side or the thumb side.

3) If the ridges flow in from the little finger side this would be an 'ulnar' loop.

4) If the ridges flow in from the thumb side this would be a 'radial' loop.

WHORLS All whorls have at least

two deltas.

A plain whorl has at least one ridge that makes a complete circle

The ridge can be in the shape of a spiral or an oval.

ARCHES

The Arch pattern is made up of ridges lying one above the other in a general arching formation.

The tented arch pattern consists of at least one upthrusting ridge, which tends to bisect superior ridges at right angles, more or less.

Basics

All fingerprints are divided into one of the three general patterns: loops whorls or arches.

The individuality of a fingerprint is determined by a careful study of ridge characteristics

Latent (invisible) fingerprints are produced when you touch a smooth surface and transfer an impression of your finger with sweat and oils

The Henry System

In 1901 – the original classification system used for fingerprints was developed by a man named Henry.

He converted all 10 fingers into a series of letters and numbers.

Both hands could be expressed as a fraction.

Problem was the system was designed for only about 100,000 sets of prints.

The number of people exceeded the system very quickly.

FBI System

By adding extensions and expanding the original Henry System, the FBI was able to create a limitless system for comparing fingerprints.

This system provides the examiner with a more limited pool of candidates from which to examine for matches.

Henry System Basics

System is based on the presence of whorls

Whorls on first pair is 16 on second – 8, third pair -4, fourth – 2 and last pair value of 1

Any finger that has an arch or loop is assigned a 0.

After all the fractions are added a value of 1/1 is added to the total for the final fraction

R Index R Ring L Thumb L Middle L Little 1

R thumb R Middle R Little L Index L Ring 1

16 0 0 0 0 1 = 17

0 8 0 0 0 1 8

Integrated Automated Fingerprint Identifcation System (IAFIS)

Ability of the computer to scan and digitally encode fingerprints

The encoding allows minutiae to be rapidly scanned

Can screen a set of 10 prints against a file of 500,000 sets of 10 prints in .08 seconds

Ridge endings (terminations)

Branching of ridges (bifurcations)

Screen out imperfections in latent prints

Can send prints immediately to FBI database

DETECTING FINGERPRINTSLocating fingerprints

Three kinds of crime scene prints:

Visible – can be seen without technology

Latent – not visible without some technology

Plastic – impressions made in soft materials such as soap, wax or putty

Visible and plastic are easy to find but latent is more difficult

Different surfaces require different visualizing methods

Hard non-porous surfaces (glass, tile, painted wood) require visualizing powders or Super glue

DETECTING FINGERPRINTS Soft and porous surfaces

(cloth, paper, cardboard) require chemical treatment

Can use RUVIS (Reflected Ultraviolet Imaging System) which locates prints on soft surfaces without the use of chemicals with UV light

DEVELOPING LATENT PRINTS POWDERS:

Adhere to perspiration and body oils

Almost any color – grey and black being most common

Grey – aluminum dust

Black –carbon or charcol

Magnetic – charged

Fluorescent – glow under UV light

FUMING:

Iodine – iodine sublimates when heated giving off fumes.

The fumes adhere to the latent print

Old technology – does not last long print visible fades in minutes

DEVELOPING PRINTS FUMING:

Super glue (Crazy glue) can visualize a print on non-porous surfaces as well as metals, tape, leather and plastic bags

Heating the Super glue releases cyanoacrylate ester fumes

Fumes produce a white fluffy print

NINHYDRIN

The chemical reacts with amino acids to produce a purple-blue color

Usually used as an 0.6 % solution sprayed as an aerosol on porous surfaces

Takes 1 to 48 hours can increase developing by heating in an oven

Effective on paper that was 15 years old

DEVELOPING PRINTS PHYSICAL

DEVELOPER

Chemical mixture – silver nitrate based

Works even if item was wet –then dried.

Used as the “last resort” because washes away all traces of proteins

NEWEST TECHNOLOGYLaser light can detect latent

prints that fluoresce with certain components of sweat.

Alternate light sources:

High-intensity quartz halogen

Xenon-arc

LED’s (light emitting diodes)

DFO (1,8-diazafluoren9-one)

Chemical works with alternate light sources

PRESERVING DEVELOPED PRINTS

Once a print is developed it must be preserved as evidence

STEP ONE: photograph developed print

STEP TWO is determined by the size of the object the print is on

If the object the print is on is small – the entire object should be taken to the laboratory

If the object is too large - then the developed print must be “lifted”.

Can use special clear tape to lift a print developed with a powder

Tape with print is placed on a card with good background contrast

DIGITAL IMAGING

Lifted fingerprints are not usually in perfect condition – making analysis even more difficult

Digital imaging programs can now enhance the lifted/partial prints to make identification more accurate

Digital imaging converts a fingerprint image into pixels

Can be done with a scanner or digital camera