Fingerprints Ms Clark PVMHS

Student objectives Discuss the history of fingerprints. Describe the system of anthropometry and the role Alphonse Bertillon plays in it. Describe the latest technologies in fingerprint identification. Discuss the role of AFIS or IAFIS in criminal investigation. Describe 3 basic types of fingerprints. Describe the shape of a delta within a fingerprint & label a delta on a fingerprint diagram Compare the number of deltas found in an arch, loop, and whorl pattern. Describe any changes that may occur to fingerprints over time. Describe the effect of someone trying to alter their fingerprints.

Student objectives Demonstrate how to take a ridge count on a fingerprint. Compare fingerprints of: Identical twins Brother and sister Family members Discuss the reliability of fingerprint evidence. Define with an example each of the following types of fingerprints: Latent Patent Plastic Compare and contrast a plastic print with a patent print. Given a partial fingerprint and several suspect fingerprints, identify which suspects fingerprint is consistent with the one found at the crime scene. Use 5 different reference points to confirm the match. Demonstrate how to properly collect fingerprint evidence. Demonstrate how to lift a latent fingerprint.

Labs: Lifting prints Preparing 10 cards Identifying unknown prints

Fingerprints Part I

History of fingerprints 1883—Alphonse Bertillon, a police officer and statistician, invented a system of body measurements that was used to identify criminals. 1901 - Sir Edward Henry established the first fingerprint classification system in Britain. Also credited with introducing police dogs to the London police force. 1903 - First official use of fingerprints in the United States (New York City Civil Service Commission). 1924 - FBI consolidates over 800,000 fingerprint files from across the United States. 1975 - The FBI introduces the Automated Fingerprint Identification System (AFIS). This system allows the computerized scan of fingerprints.

What are fingerprints? All fingers, toes, feet, and palms are covered in small ridges . Ridges help us grip objects. Ridges are arranged in connected units called dermal, or friction ridges. Fingers accumulate natural oils and dirt. Fingers leave prints on objects we touch. A fingerprint is an individual characteristic. Even identical twins have unique fingerprints. Fingerprints have general characteristic ridge patterns that permit them to be systematically classified.

Structure of Skin Your skin has 3 layers: Epidermis – the top layer of skin that you can see and touch. Dermis – the middle layer of skin that contains all your blood vessels and sensory receptors. Hypodermis – the bottom layer of skin, primarily made up of adipose (fat) tissue. Connects the skin to the muscles underneath. The bottom layer of your epidermis is called the stratum basale. The cells in this layer are constantly growing -undergoing mitosis (cell division). The top layer of the dermis is called the papillary layer. The papillary layer has projections called dermal papillae that form your fingerprints. The papillary layer and the stratum basale are touching.

Your turn: Label the following structures on a skin diagram: Epidermis Sweat pores Stratum basale Dermis Papillary layer Dermal papilla Sweat gland Oil gland Hair follicle Hypodermis

Formation of Fingerprints Fingerprints begin forming near the 10th week of pregnancy The basal layer of the epidermis grows faster than the neighboring papillary layer of the dermis. This causes the basal layer to buckle and fold in several directions, forcing the papillary layer to fold into complex shapes called dermal papillae.

Characteristics of Fingerprints Core (the center of a whorl or loop) Deltas (triangular regions near a loop) Ridge count Counting from the core to the edge of the delta Distinguishes one fingerprint from another

3 basic types of Fingerprints ARCH About 5% WHORL About 30% LOOP About 65% -of the population

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

Arches

Loop A loop must have one or more ridges entering and exiting from the same side. 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 it is on the right hand? Left hand?

Whorl A plain or central pocket whorl has at least one ridge that makes a complete circuit. A double loop is made of two loops. An accidental is a pattern not covered by other categories. Whorls have at least two deltas and a core. Types Plain Central Pocket Double Loop Accidental

Whorls

Ridge Characteristics Minutiae—characteristics of ridge patterns Ridge ending Short ridge Dot or fragment Bifurcation Double bifurcation Trifurcation Bridge Island Enclosure Spur

Your turn: Take one white balloon & an ink pad. Blow balloon up part way, ink finger and place your print on the balloon. Do this for 2-3 fingers Now blow up the balloon all the way. Identify 10 minutiae points on each fingerprint using a felt tip pen. 3 2 1