Download
1 / 40
400 likes | 410 Views
FORENSIC SCIENCE Fingerprints. History. 3000 years ago: Chinese used fingerprints to sign legal documents
E N D
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.)
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
AFIS Automated Fingerprint Identification System AFIS is one of the three significant electronic databases for law enforcement purposes. There are two types of files: • Knowns: Contains prints of known individuals • Forensic files: Consists of images from unsolved cases
Fundamental Principlesof Fingerprints • A fingerprint is an individual characteristic. • A fingerprint will remain unchanged during an individual’s lifetime. • Fingerprints have general characteristic ridge patterns that permit them to be systematically classified (arch, loop or whorl).
Ridge Characteristics Minutia--lines of the fingerprint • ridge ending • bifurcation • short ridge island • dot or fragment island • enclosure
MINUTIA RIDGE ENDING BIFURCATION
MINUTIA SHORT RIDGE DOT or FRAGMENT ISLAND ENCLOSURE
MINUTIA Exits: describes the direction of lines coming in or out Deltas: triangle with ridges radiating outward in 3 directions. How many exits and deltas are present?
Fingerprint Patterns • Arch • Loop • Whorl
Arch An arch has 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. Summary: • Exits: 2 • Deltas: 0 Least common pattern (5%)
Arch • Summary: • Exits: 2 • Deltas: 0
Loop A loop must have one or more ridges entering and exiting from the same side it began. Loops must have one delta. Summary: • Exits: 1 • Deltas: 1 *Most common pattern (60%)*
Loop • Exits: 1 • Deltas: 1 *Most common pattern (60%)*
Whorl A whorl has at least one ridge that makes a complete circuit and two points of delta Summary: • Exits: 0 • Deltas: 2
Whorl Summary: • Exits: 0 • Deltas: 2
Fingers 2 8 2 1 16 8 4 1 16 4
Dactyloscopy • The practice of using fingerprints to identify someone.
Tracking Down Fingerprints • Patent Prints • Plastic Prints • Latent Prints
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.
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.
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.
Latent Prints 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.
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.
Lifting Latent Prints (cont) • Powders--adhere to both water and fatty deposits. Choose a color to contrast the background. • 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.
Lifting Latent Prints (cont) 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.
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.
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.
Bertillon’s Embarrassing Moment Bertillon reluctantly agreed to add fingerprints to his bertillonage profile. However, he added only those of the right hand.
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.
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.
Homework Questions • What is dactyloscopy? • List and describe (exits and deltas) of the 3 fingerprint patterns. • Draw the following minutia: • bifurcation • short ridge / island ridge • eye/island enclosure • Identify and describe the 3 kinds of fingerprints (not patterns). • List the different ways in which we can lift prints. What color do prints appear for each method?
