Fingerprints

History 3000 years ago… Chinese used fingerprints for legal papers 1880 Henry Fauld –first to use FP to ID criminals 1897 Sir Edward Richard Henry- -developed Henry classification - based on all 10 prints - number/location of whorls

Skin Epidermis- outer layer, no blood supply Dermis-internal layer- sweat glands that produce water, salts, oils Papillae- at boundary of dermis and epidermis Prints- made of mostly water, salts, oil

Cross Section of Skin

AFIS Automated Fingerprint Identification System

Matching points Also known as: - Minutiae - Galton points Based on types of ridges Match ridges from a known print with an unknown print.

Types of Ridges Ending ridge Bifurcation (fork) Enclosure Short ridge Dot Eye (island) Bridge Double bifurcation Trifurcation

Fingerprints Friction ridges help human grip things Identical twins have different fingerprints. Fingerprints do not change over your lifetime. Scarring, etc can be used for ID

Deltas Delta- ridge that diverges Loops have one delta Whorls have 2 deltas Arches do not have deltas.

Types of Fingerprints 1. Arch 2. Whorls 3. Loops

Arches Arches (no core or delta) Plain Tented

Whorls One or more ridges make complete circles Two deltas and at least one core

Loops Radial- loop opens to thumb Ulnar - loop opens to pinky side

Pores Found randomly along the ridges Produce sweat Chemicals in sweat make the fingerprint that is left behind Pore location can be used to identify the person.

Process of Identification Get prints of all ten fingers from a person in question (suspect, victims, police, etc..) Ways to get the 10 prints Traditional ink and paper Roll colorless chemical on treated paper… chemicals react and the print becomes visible (newer) Live scan: roll prints on glass over video camera. Image is turned into digital information (newer)

Quality of prints Quality affected by: Skill and experience of person taking the print Cooperation of person giving the print Damaged skin on people who work w/ their hands Rigor mortis Decomposition, burned bodies

Types of Prints 1. Visible (patent) 2. Plastic 3. Latent Bloody prints Tacky paint Putty Clay Soap 3. Latent Invisible Deposit sweat and oil

Methods to Develop Prints Black powder Magnetic powder Iodine fuming (good on paper) Silver nitrate Ninhydrin ( for prints on paper) Super glue (=cyanoacrylate) Stickyside ™powder

Locating prints Shine flashlight at oblique angle Gloves may leave impression Less obvious places: under toilet seats, toilet handles, tabletops, dresser drawers, surface of dinner plates, back of rearview mirrors, trunk lids of cars Use someone familiar w/ scene to tell if anything is different about the area

Equipment Ultraviolet light (black light) Laser Alternate light source Some substances will glow when exposed to UV Ex. LSD– bluish-white Ex. Certain fingerprinting powders glow under UV Laser Alternate light source powerful light causes some materials to fluoresce or luminesce

Daubert Hearings Fingerprint experts need to convince a judge that the methods used are valid. Daubert standards: Has the expert’s scientific method been tested? Has the expert’s method been the subject of peer review and testing What is the actual or potential rate of error? do other scientists generally accept the expert’s methods?

Odds and Ends If AFIS is used to locate a match, the final identification must be done by a human Palm prints can also be used Latent prints can often be developed years later as long as they don’t become wet Fingerprints made from soot, insulation, face powder are easily destroyed Prints made from blood, ink, oil can last longer