FORENSIC SCIENCE CHAPTER 4 Fingerprints and Footprints.

FORENSIC SCIENCECHAPTER 4

Fingerprints and Footprints

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History

William Herschel Early 1880’s Used Chinese custom of using thumb print to sign

legal documents Had natives of India use right thumb to sign contracts

http://science.howstuffworks.com/fingerprinting3.htm

History

Alphonse Bertillion First attempt at personal identification 1883 Body measurements & Portrait Parlé

Used theory that dimensions of body remained fixed from age 20 and older

No two skeleton sizes were alike Took 11 measurements – height, reach, width of

head Portrait Parlé – a verbal description of physical

characteristics given by an eye witness Most accurate for 20 years

History

Henry Fauld 1880 Skin ridge patterns – used to identify criminals

First person to solve a crime using prints Tried to “sell” this concept to Scotland Yard –

they rejected

History

Francis Galton 1892 Published the book, Finger Prints Proposed the idea of patterns

and suggested a method of recording Loops, arches, whorls

Demonstrated that no two prints were alike

History

Dr. Juan Vucetich Argentinian police officer 1891 Devised first workable classification system for

logging fingerprints

History

Sir Edward Richard Henry 1897 Proposed another method of classification

Most English speaking countries use a variation of Henry’s system

In 1901, adopted by Scotland Yard

History

1901 – US adopts first official use of fingerprinting (New York City Civil Service Commission)

1924 – FBI adopts fingerprinting1999 – US v Byron C. Mitchell

The first case in which fingerprints were questioned. Judge ruled, according to Daubert, that they were admissible

Principles of Fingerprinting

1. Fingerprints are an individualistic characteristic Study the ridge characteristics (minutiae)

Identity, number, location (as many as 150 individual ridges on one fingerprint!)

Point by point comparison Originally needed 8-16 exact matches 1973 – no numerical requirement – based on

experience/knowledge of expert Ridges (handout)

Bifurcation Ridge ending Enclosure Short ridge (Island) Ridge Dot Ridge crossing

Principles of Fingerprinting

Principles of Fingerprinting

Principles of Fingerprinting

2. Fingerprints do not and cannot change Fingerprints are friction skin ridges

Developed in womb Purpose to give firmer grasp and resistance to slip

Principles of Fingerprinting

Skin – cells Surface = epidermis Inner skin = dermis Dermal papillae – boundary layer under the epidermis

– shape of this layer determines ridge patterns Remains unchanged throughout life!

Principles of Fingerprinting

Change prints? Must damage dermal papillae – about 1-2mm beneath

skin John Dillinger case

Fingerprint? Oils and perspiration are transferred from finger to a

surface leaving a print Normally “invisible” - latent

Principles of Fingerprinting

3. Fingerprints can be classified by ridge patterns Three classes

Loops (60-65%) Whorls (30-35%) Arches (5%)

Principles of Fingerprinting

Loops Ridge enters from one side,

curves, and exits same side If loop opens toward pinky =

ulnar loop If loop opens toward thumb =

radial loop Core = center of loop

Principles of Fingerprinting

Whorls ALL have two deltas! 4 groups

Plain Central Pocket Loop Double Loop Accidental

Principles of Fingerprinting

Plain Whorl Central Pocket Loop Double Loop

Principles of Fingerprinting

Arches Enters one side, exits other NO deltas!! Two groups

Plain arch Tented arch

Principles of Fingerprinting

Plain Arch Tented Arch

Fingerprint Classification

Henry System 1901 Converted ridge patterns into a series of numbers and

letters to form a fraction Could only classify up to 100,000 sets

Fingerprint Classification

FBI System (Primary Classification) Pair up finger in following manner:

R.Index R. Ring L.Thumb L.Middle L.Little R.Thumb R.Middle R.Little L.Index L.Ring Look for whorl pattern If whorl is found in:

First pair = give a 16 Second pair = give an 8 Third pair = give a 4 Fourth pair = give 2 Last pair = give 1 No whorls = 0

Fingerprint Classification

FBI System (cont) Total the values for numerator and denominator, add

one to both = fraction This is a ten finger scheme – useful only when a full

set of prints are available!!

Fingerprint Classification

AFIS Automated Fingerprint Identification System 1970 Computer can scan and digitally encode prints Stores as a geometric pattern Compare degree of correlation Can make thousands of comparisons in one

second! “Hit” prints are also visually examined

Fingerprint Classification

AFIS (cont) No final decision Allows search against entire file not just suspects

Fingerprint Classification

IAFIS Integrated Automated Fingerprint Identification

System National system maintained by FBI

Livescan

Livescan – an inkless device that captures the digital images of fingerprints and palm prints and electronically transmits images to AFIS A fingerprint record is made in minutes!

Prints as Evidence

Locate PrintsDevelop PrintsVisualize PrintsPreserve Prints

Locating Prints

Three kinds of prints Visible

Fingers touch surface after they have been in contact with a colored material (ink, blood)

Plastic Ridge impressions left on soft material (soap,

wax, dust) Latent

“Invisible” – Transfer of oils and perspiration MUST be found and visualized!!

Locating Prints

RUVIS – Reflected Ultraviolet Imaging System Can locate prints on most non-absorbant surfaces

without aid of any other treatment method Aims UV light at surface

Developing Prints

Methods Available: Powders Iodine Fuming Ninhydrin Physical Developer Super Glue Fuming

Developing Prints

Powders – Non-Porous Surfaces Adhere to perspiration residues and/or oil

deposits Want best color contrast:

Gray (Al dust) – for dark surfaces Black (charcoal) – for light surfaces

Magnetic powders Spread over surface with magnet (rough)

Fluorescent powders Fluoresce under UV

Developing Prints

Chemical Treatments Iodine fuming

Porous and non-porous surfaces! Heat solid iodine crystals Sublimes (solid gas) Vapors visualize prints – React with either fatty oils or

water from sweat NOT permanent – will fade once sublimation stops

Can “fix” prints by spraying with a starch solution

Developing Prints

Chemical Treatments (cont) Ninhydrin (triketohydrindene hydrate)

Porous materials – paper, cardboard, envelopes Reacts with amino acid deposits Turns a purple-blue color Appear within 1-2 hours after spraying Heating (80-100°C) the print speeds up process DFO (1,8-diazafluoren-9-one)

Newer substitute for ninhydrin Has been shown to develop 2.5 times more latent

prints on paper than ninhydrin

Developing Prints

Chemical Treatments (cont) Physical Developer

Silver nitrate based liquid Good on porous articles that were once wet

Developing Prints

Super Glue Fuming 1982 Works on non-porous materials (plastic bags, tape) Super Glue = 98.99% cyanoacrylate ester Heat glue – fumes adhere to print White prints

Developing Prints

Visualize Prints

Laser Light Perspiration contains components that

fluoresce in laser light Prints are then photographed with special

filters Argon-ion lasers

Blue-green light output Limitation – Perspiration in prints are often in too

small of a quantity to be observed with this light

Visualize Prints

Alternate Light Sources Has replaced laser lights Quartz Halogen Xenon arc LEDs PORTABLE!!!

Preservation of Prints

PhotographTransport

Entire Object Cover with cellophane and transport

Lifting Adhesive tape Hinged lifters

QUIZ

Footwear Evidence

Two Types 3-dimensional 2-dimensional

Footwear Evidence

3-dimensional Those that remain after the shoe has permanently

deformed surface Exterior surfaces (sand, soil, snow) Quality

Affected by: Amount of moisture Contaminants (sticks, stones, debris) Composition of material

Footwear Evidence

2-dimensional Made on non-giving surfaces (tile, wood, paper,

linoleum) Visible or latent

Significance of Footwear Evidence

Significance of footwear evidence (in other words – why collect footwear evidence?) To identify footwear

Look at class and individual characteristics To prove presence at scene To prove participation in a crime

To eliminate footwear May exonerate suspect

To determine shoe brand Footwear databases - FBI

Significance of Footwear Evidence

To determine shoe size To determine gait characteristics

Gait measurements can indicate:1. Stride Length, which can prove if:

• Carrying something = short stride• Running = long stride• Normal walking = normal stride

Significance of Footwear Evidence

Gait measurements can indicate:2. Angle at which toe points when walking3. If suspect walks with a limp or hitch

Measuring distance from one step to another

4. If suspect is a “Toe” or “Heel” walker Distribution of weight

5. Width between steps6. Approximate size of suspect:

Small but not deep print = short, light Small but deep = short, heavy Large, not deep = tall, light Large, deep = tall, heavy

Using Footwear as Evidence

Steps: Locate Recover Examine Compare

Locate Footwear Evidence

Locate Some obvious – Visual prints (bloody) Latent

Slow search Same search patterns discussed last chapter Use oblique lighting in a dark room

Items to consider: Glass, paper, dust

Recover Footwear Evidence

Recover Photograph, Photograph, Photograph!! 2-dimensional:

Electrostatic Lifting device High voltage power source to create a static electrical charge

that enables the transfer of the print• Used first – will not harm evidence• Very fragile

Dust/Lift Contrasting colors

Footwear Evidence

Recover 3-dimensional:

Casts Dental stone – gypsom product Will harden in approx 20 min

Examine Footwear Evidence

Examine Design Physical size and shape Wear (position and degree) Individual characteristics

Cuts, scratches, tears

Compare Footwear Evidence

Compare Crime scene to known shoes Side-by side comparisons Superimposition method