Fingerprints

Fingerprinting System of identification based on the classification of finger ridge patterns

Fundamental Principles of Fingerprints No two persons have identical ridge patterns. A fingerprint remains unchanged during a person’s lifetime. Fingerprints have general ridge patterns that can be systematically classified.

What are Fingerprints? An impression left on any surface that consists of patterns made by the ridges on a finger Ridge: appears dark in an images Valley: appears light in an image

Giant Balloon Fingerprints Activity Giant Balloon Fingerprints

Human Skin The epidermis (outer layer) and dermis (inner layer) determine the form and pattern of ridges on the surface of skin Fingerprints develop in the human fetus (starting the 10th week) Other prints: palms of the hands, soles of feet, lips, ears

Ten Card A form used to record and preserve a person’s fingerprints

Activity: Making a Ten Card Use ink strips to print each finger on the handout provided.

Fingerprint Patterns Three classes: Loops Whorls Arches

National Population (%) Fingerprint Data Fingerprint Type Total # Classroom Total # Classroom % National Population (%) Loop Whorl Arch

National Fingerprint Data National Population: Loops (65%) Whorls (30%) Arches (5%)

Fingerprint Patterns

Ridge Characteristics

Minutiae Minutiae: points where print ridges come together or end Minutiae points considered to be the “uniqueness” of an individual Also called “Points” FBI have found that no two individuals have more than 8 common “Points”

Minutiae Points

Latent Fingerprints

Activity: Make a Latent Print Follow instructions to make a latent print on a clean surface.

Types of Fingerprints Patent (Visible) Print Impressed (Plastic) Print Latent Print

Patent (Visible) Print Finger comes in contact with medium (blood, dirt, ink, grease) and leaves visible impression

Plastic (Impressed) Prints Indentations left in clay, wax, paint, soap, putty or other soft pliable surfaces Can be viewed or photographed

Latent Print Fingerprint made by the deposit of oils and/or perspiration Invisible to the naked eye Made visible by dusting, fuming or other chemical reagents

Detection of Latent Prints Fingerprint powders (colored, magnetic, fluorescent dyes) Iodine Fuming Ninhydrin Cyanoacrylate (superglue) fuming Silver Nitrate

Detection of Latent Prints

Studying a Latent Print

Studying a Latent Fingerprint Using the fingerprint brush and black powder, lightly dust the fingerprint (use a circular motion) Press and lift the print off of the surface using clear tape. Tape your latent print into your lab notebook. Identify your print pattern as either a loop, arch or whorl. Repeat with magnetic powder and pen.

Latent Print Recovery Lab Using chemicals to detect a latent print: Type How does it work? Test Sample Safety Warning Cyanoacrylate Reacts with amino acids Glass Slide Do not inhale or get on your skin Ninhydrin Reacts with amino acids (proteins) found in sweat Paper Iodine Crystals Reacts with oils Toxic to inhale or ingest

Analysis of Lab: For each station, write a paragraph that includes the following ideas: Explain the procedures used to recover the print. Describe what you observed. What other surfaces do you think this method would work on?

Automated Fingerprint Identification System (AFIS) In 1999, state AFIS computers were fully linked with the FBI database Contains nearly 50 million fingerprint records Each fingerprint scanned; digital minutiae data stored in computer

How is AFIS used? Unknown print is scanned and entered into computer Computer searches AFIS system and produces a list of file prints that match closest with search print (takes 2 hours) Fingerprint expert examines prints and makes final verification on print’s identify

Mobile Fingerprint Identification Used by police officers in the field to search AFIS and get a positive identification on a suspect.

Fingerprint FAQs Fingerprints dissolved by acid will grow back Scars on fingers make prints even more unique