FORENSIC SCIENCE Fingerprints

History of Fingerprints Before prints, identification was done by anthropometry. Alphonse Bertillion was the one to develop this system of using precise body measurements. It wasn’t until 1903, that anthropometry had its worst setback with the wrongful conviction of Will West. One of the 1st US cases was in 1911, in NYC, Caesar Cella accused of robbery. Several marks of dirty fingers on the window frame matched Cella’s.

What is a Fingerprint? During the 3rd & 4th months of fetal life the sweat glands on the palm of the hands and soles of the feet form ducts which exit out the body and onto the skin, forming small pods. During this period these pods eventually link together to form ridges which you observe on the surfaces today. No two people have the same fingerprints (even identical twins!!!) Your prints do not change with age!

Fundamental Principles of Fingerprints 1) A fingerprint is an individual characteristic. 2) A fingerprint will remain un-changed during an individual’s lifetime. 3) Fingerprints have general characteristics ridge patterns that permit them to be systematically classified.

Anatomy of Skin Once formed prints do NOT change, unless deformed by deep scarring. If a cut reaches deep into the dermal tissue it will leave a scar, but that mark can still be unique to your finger. Acid will not work either (Ex: John Dillinger) Skin Layers

Left behind….. When a person touches an object a print of the ridge is left behind by oils from the glands. This is what provide us with the means to identify people. There are 3 basic patterns: Loops(~60%), Whorls(~30%), and Arches(~10%)

Loop A loop must have one or more ridges entering and exiting from the same side it began. Loops also must have one delta. Types: Radial--loop open towards the thumb (~5%) Ulnar- -loop open towards the pinky (~60%) (You MUST know what hand to id type of loop!)

Whorl The ridges re-curve around 2 deltas. A plain whorl – have at least one ridge that makes a complete circuit and 2 deltas. A central pocket whorl – some of the ridges form a loop that re-curves the central whorl.

C P W

Additional Types of Whorl Patterns Double loop – 2 separate loops present, which sometimes surround each other. (double-loop whorl) Accidental – any pattern which does not conform to any of the previous patterns.

Double Loop and Accidental Images

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 have NO deltas. Plain arch – the ridge enters, rises, and exits smoothly. Tented arch – the ridge in the center thrusts upward to give an appearance of a tent.

                                        

Identifying Prints The latest innovation in fingerprinting is all digital! The fingers are pressed against a glass and scanned to a computer. AFIS (Automated Fingerprint Identification System) is a database of prints that are already scanned in the system and set up by the FBI.

Ridge Characteristics Within the patterns are small marks called: Minutia--lines of the fingerprint ridge ending bifurcation short ridge island enclosure

MINUTIA BIFURCATION RIDGE ENDING *Two of the more common minutia patterns.

What Next….. Just the presence of these minutia does not individualize a print. It is the exact type of minutia as well as the location that individualizes a print. Therefore, you can conclude if you are comparing 2 prints and they have the same markings…the same place…They are the SAME PRINT and SAME PERSON!!! Courts need a certain amount of minutia matches to be considered a concrete match.

Types of Prints There are three main types of prints found at a crime scene: Latent Prints are those that are “hidden” and are not visible to the naked eye. These prints consist only of the natural secretions of oil from the human skin and require treatment to cause them to become visible. Visible Prints are those that are found on colored material like blood, paint, grease, ink, etc. Plastic Prints are those that are found on a soft material like wax, soap, dust, putty, etc.

Lifting Latent Prints 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. Iodine--fumes react with oils and fats to produce a temporary yellow brown reaction.

Iodine Fingerprint

Lifting Latent Prints (cont) 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.

Ninhydrin Fingerprint

Cyanoacrylate Fingerprint

Other Prints Ears--shape, length and width Face--pictures being used in Florida to find criminals Voice--electronic pulses measured on a spectrograph Feet--size of foot and toes; lines of the feet Shoes--can be compared and identified by type of shoe, brand, size and year of purchase

Other Prints Palm--lines can be identified and may be used against suspects.

Other Prints Foot Prints are taken at birth as a means of identification for infants.

Other Prints Teeth--bite marks are unique and can be used to identify suspects. These imprints were placed in gum and could be matched to crime scene evidence.

Let’s Practice…. Let’s see how well you do at identifying specific minutia…