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FORENSIC SCIENCEFORENSIC SCIENCEFingerprintsFingerprints

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History 3000 years ago: Chinese used fingerprints to

sign legal documents 1880: Henry Faulds suggested that friction

ridges be used to identify criminals. (Faulds actually wrote a letter to Charles Darwin regarding fingerprinting but Darwin thought that his cousin Galton would find it more interesting.)

Several years before Bertillon: William Hershel required natives of India to sign contracts with the imprint of their right hand. (There was a dispute between Faulds and Hershel over which of the two was the first to propose fingerprints as a method of identification.)

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History cont. 1883 - Bertillon introduced anthropometrics 1891 – Dr. Juan Vucetich uses the work of Galton

to refine a classification system (still used in Spanish speaking countries).

1892 – Galton describes loops, whorls, and arches 1897 – Sir Edward Henry develops the

classification system that is used in the U.S. 1924 – FBI Identification Division Established

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AFISAutomated Fingerprint Identification System

AFIS is one of the three significant electronic databases for law enforcement purposes.

There are two types of files:1. Knowns: Contains prints of known

individuals2. Forensic files: Consists of images from

unsolved cases

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Fundamental Principlesof Fingerprints

A fingerprint is an individual

characteristic.

A fingerprint will remain unchanged

during an individual’s lifetime.

Fingerprints have general

characteristics ridge patterns that

permit them to be systematically

classified.

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Ridge Characteristics

Minutia--lines of the fingerprint

ridge ending

bifurcation

short ridge island

dot or fragment island

enclosure

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MINUTIA

RIDGE ENDINGBIFURCATION

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MINUTIA SHORT RIDGEDOT or FRAGMENT

ENCLOSURE

ISLAND

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In Court Courts require different amounts of matching

points of minutia

UK requires 16 pointsAustralia requires 12 pointsFBI requires 12 pointsU.S. courts require 6-8 points

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Arch An arch has friction

ridges that enter on one side of the finger and cross to the other side while rising upward in the middle. They do NOT have type lines, deltas, or cores.

Types Plain Tented

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Loop A loop must have one or more

ridges entering and exiting from the same side it began. Loops must have one delta.

Types Radial--opens toward the thumb

Ulnar--opens toward the “pinky” (little finger)

Which type of loop is this, if on the right hand? Left hand?

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Whorl A plain or central pocket

whorl have at least one ridge that makes a complete circuit. A double loop is made of two loops and an accidental is not covered by other categories.

Types Plain Central Pocket Double Loop Accidental

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Primary Identification Numbers

1. right 2. right 3. right 4. right 5. right thumb index middle ring little

16 16 8 8 4

6. left 7. left 8. left 9. left 10. left thumb index middle ring little

4 2 2 1 1

Fingers are numbers 1 through 10 starting with the thumb on the right hand and continuing through with the thumb on left hand.Each finger is then given a point value as seen in the chart below.

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Primary Identification (cont)

2. right 4. right 6. left 8. left 10. left index ring thumb middle little

16 8 4 2 1

16 8 4 2 1

1. right 3. right 5. right 7. left 9. left thumb middle little index ring

Set up a ratio of even numbered fingers over odd numbered, adding one in both the numerator and denominator.

+ 1

1

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Fingers

1

1 2 2

416

16 88

4

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Tracking Down Fingerprints

Patent Prints Plastic Prints Latent Prints

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Patent Prints

Patent prints occur when a substance such as blood, ink, paint, dirt, or grease on the fingers of the perpetrator of a crime leaves behind a readily visible print.

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Plastic Prints Plastic prints have a three-

dimensional quality and occur when the perpetrator impresses a print into a soft substance such as wax, putty, caulk, soap, cold butter or even dust.

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Latent Prints Latent fingerprints are those that

are “hidden” and are not visible to the naked eye. These prints consist only of the natural secretions of human skin and require treatment to cause them to become visible.

Most secretions come from three glands: Eccrine--largely water with both inorganic (ammonia,

chlorides, metal ions, phosphates) and organic compounds (amino acids, lactic acids, urea, sugars)

Apocrine--secrete cytoplasm and nuclear materials Sebaceous --secrete fatty or greasy substances.

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Skin Layers

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Lifting Latent Prints Here’s where the chemistry comes

in…….. Developing a print requires chemicals

that react with secretions that cause the print to stand out against its background. It may be necessary to attempt more than one technique, done in a particular order so as not to destroy the print.

Powders--adhere to both water and fatty deposits. Choose a color to contrast the background.

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Lifting Latent Prints (cont) Iodine-- fumes react with oils and fats to produce a

temporary yellow brown reaction. Ninhydrin--reacts with amino acids to produce a purple

reaction. Silver nitrate--react with chlorides to form silver chloride,

a material which turns gray when exposed to light. Cyanoacrylate--”super glue” fumes react with water and

other fingerprint constituents to form a hard, whitish deposit.

In modern labs and criminal investigations, lasers and alternative light sources are used to view latent fingerprints. It was first used by the FBI in 1978. Since lasers can damage the retina of the eye, special precautions must be taken and a filter used.

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Iodine Fingerprint

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Ninhydrin Fingerprint

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Cyanoacrylate Fingerprints

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Will West & William West

May 1, 1903 – Will West went to Leavenworth Penitentiary in Kansas. The clerk thought that he looked familiar but Will denied ever being there. Coincidentally, there was another inmate named William West. They looked very much the same and had the same Bertillon anthropometric measurements but they denied ever knowing each other.

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Will West & William West

Fingerprints helped authorities distinguish between the two Wills. So much for measuring the width of a person’s head. Leavenworth immediately dumped the Bertillon anthropometric system and switched to a fingerprint system.

P.S. This wasn’t just a bizarre coincidence. A report in the Journal of Police Science and Administration in 1980 revealed that they were indeed identical twins and each wrote letters to the same brother and five sisters and the same Uncle George.

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Bertillon’s Embarrassing Moment

Bertillon reluctantly agreed to add fingerprints to his bertillonage profile. However, he added only those of the right hand.

Big mistake!

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This is where Mona Lisa comes in…

On August 21,1911, Leonardo da Vinci’s famous painting Mona Lisa was stolen from the Louvre Museum in Paris. The thief left a clear thumbprint on the glass that had protected the masterpiece. No system of classification had been devised yet so Bertillon and his assistants spent several months digging through his files. They found no match.

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Mona Lisa cont.

Two years later police apprehended the thief, Vicenzo Perugia. His prints matched the ones found at the newest crime scene. It turns out that Perugia’s prints were among those in Bertillon’s possession the whole time. No match had turned up because the print found at the scene of Mona Lisa was from Peruglia’s left thumb and Bertillon’s files contained only that of Peruglia’s right thumb.

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It’s thumbthing to think about…