Fingerprints Forensic Science

Al Capone’s Fingerprints

History of Fingerprints• 1000 BC – Chinese sign legal documents with fingerprints.

• Not sure if they knew the significance

• 1685 – Marcello Malpighi at the University of Bologna recognizes fingerprint patterns

• loops, whorls, and arches

• 1823 – Purkjne identifies 9 basic fingerprint patterns, forming the basis of today’s classification.

• 1858 – Herschel makes natives in Bengal, India sign documents with a hand imprint.

• He notices that prints do NOT change over time.

• 1883 – Bertillon System is developed

Bertillon System

• First systematic attempt at personal identification

• Consisted of:– precise measurements of

body parts (anthropometry)– Detailed description of the

subject– Full length photograph

• System was Flawed…

Case Study of Bertillon System • Will West Case: 1903• Will West went to Leavenworth Penitentiary

in Kansas.• The records clerk thought he looked familiar,

but he denied every being incarcerated. • Prison officials investigated and found another

William West at Leavenworth with the exact same Bertillon measurements as Will West.

• The two Wests denied being brothers or having any knowledge of each other.

• Fingerprints helped distinguish between the two Wests.

• The Bertillon System was immediately dumped

History of Fingerprints Cont…• 1880 – Faulds (a surgeon) writes that fingerprints can

be used for personal ID. • 1892 – Galton published the first text book

on fingerprints (“Finger Prints”) – Described patterns, established that no two prints

were identical, and prints remained unchanged throughout life.

• 1899 – Sir Edward Henry devises a classification on 5 types of prints– A modified system of the Henry classification system is used

by the FBI today in the US.• 1910 – Thomas Jennings was the first person convicted

for murder in Chicago on fingerprint evidence – LANDMARK CASE.

Bertillon’s 2nd Big Mistake !

• 1910 – Bertillon adds fingerprints to his Bertillonage profile but only includes the right hand…. BIG MISTAKE!

• Case Study: 1911 – Da Vinci’s Mona Lisa was stolen.

– Left at the crime scene was a thumbprint of the left hand of the criminal.

– Bertillon did not have data for the left hand and the perpetrator was not found for another two years.

Fundamental Principles of FP

1. A Fingerprint is individual and NOT shared by two people – even twins

2. A Fingerprint will remain unchanged during an individual’s lifetime.

– John Dillinger Case Study

3. The individuality of fingerprints is NOT determined by its general shape or pattern but by careful study of the ridge characteristics. (Minutiae)

John Dillinger Case Study

• In an effort to avoid police, underwent facial plastic surgery and tried to remove his fingerprints by burning them off with acid.

• Despite his efforts… prints taken at the morgue still matched the ones on file.

Composition of Skin • Skin is composed of layers of cells

– Epidermis – closest to the surface – Dermis – inner skin – Dermal Papillae – area in between the

Epidermis and Dermis. • Determines the ridge pattern • Develops in the human fetus

• In order to change the pattern, damage would have to penetrate 1 to 2mm beneath the skin’s surface (OUCH) and then the scars would become a pattern – efforts to change are futile!

Minutiae• There are as many as 150

ridge characteristics on an average print

• Most of the time only partial prints are recovered at a crime scene

• There is no set criteria number of characteristics that must match to consider prints the same.

• Generally 8-16 matches found by an expert are considered a good match.

Three Classes of Prints1. Loops

– 65% of the population

– One or more ridges that enter from one side and curve and exit from the same side.

– Ulnar loop – opens toward the little finger

– Radial loop – opens toward the thumb

– Must have at least one delta (point of divergence.)

Delta

Three Classes Cont… 2. Whorls

– 30-35% of the population – 4 types: Plain, central pocket, double

loop and accidental – Minimum of 2 Deltas

3. Arches – 5% of population (very rare)– 2 types: plain and tented

• Since the 1970’s technological advances have made possible the classification and retrieval of fingerprints by computers.

• Use AFIS – Automated Fingerprint identification systems

Methods of Detecting Prints 1. Visible Prints – contact with

colored material such as paint, blood, grease, or ink leaves a noticeable print.

2. Plastic Print – impression left on a soft material such as putty, wax, soap, or dust

3. Latent Prints – caused by the transfer of body perspiration or oils on fingers to an object (Invisible to the eye)

• Need a developer to aid in discovery

Developers for Nonporous/Nonabsorbent Surfaces

• Super Glue – cyanoacrylate reacts with sodium hydroxide releasing a vapor that binds with the amino acids forming a white latent print.

• Powder – adheres to oils and moisture in the prints making it visible. (The color of powder used, depends on the material where the print was left.)

• RUVIS – Reflected Ultraviolet Imaging System, detects print in its natural state by aiming UV light at the prints.

Developers for Porous/Absorbent Surfaces

• Iodine Fuming – iodine vapors combine with oils to visualize prints. (Must be photographed immediately…will disappear over time.)

• Ninhydrin – forms purple-blue color with amino acids present in perspiration. (Most popular method.)

• Physical Developer – silver nitrate-based chemical mixture used to visualize prints. Shown to be effective at visualizing prints that are undetected by other methods.

Fingerprint Processing • Should not be preformed at the

crime scene. • Items should be submitted to

the lab• Once latent prints are

visualized they must be permanently preserved for future comparison and possible use in court as evidence. (Usually photographed)

• Fingerprints can now be enhanced for the most accurate and comprehensive analysis using digital imaging.