Fingerprints

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

Fundamental Principles of Fingerprints 1. No two persons have identical ridge patterns. 2. A fingerprint remains unchanged during a person’s lifetime. 3. 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 An impression left on any surface that consists of patterns made by the ridges on a finger Ridge: appears dark in an images Ridge: appears dark in an images Valley: appears light in an image Valley: appears light in an image

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 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 10 th week) Fingerprints develop in the human fetus (starting the 10 th week) Other prints: palms of the hands, soles of feet, lips, ears Other prints: palms of the hands, soles of feet, lips, ears

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

Act 6-1 Study Your Fingerprint Loop Whorl Arch

Fingerprint Patterns Three classes: LoopsLoops WhorlsWhorls ArchesArches

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

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

65%5%30%

Fingerprint Patterns

Ridge Characteristics

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

Minutiae Points

Ridge EndingBifurcationShort Ridge

Latent Fingerprints

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

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

Patent (Visible) Print Finger comes in contact with medium (blood, dirt, ink, grease) and leaves visible impression 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 Indentations left in clay, wax, paint, soap, putty or other soft pliable surfaces Can be viewed or photographed Can be viewed or photographed

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

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

Detection of Latent Prints

Studying a Latent Print

Studying a Latent Fingerprint 1. Using the fingerprint brush and powder, lightly dust the fingerprint (use a circular motion) 2. Press and lift the print off of the surface using clear tape. 3. Tape your latent print into your lab notebook. 4. Identify your print pattern as either a loop, arch or whorl.

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

How is AFIS used? 1. Unknown print is scanned and entered into computer 2. Computer searches AFIS system and produces a list of file prints that match closest with search print (takes 2 hours) 3. 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 Fingerprints dissolved by acid will grow back Scars on fingers make prints even more unique Scars on fingers make prints even more unique