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Fingerprinting Why do we have fingerprints? “Friction Ridge Skin” Provides a firm grasp & resists slippage. ► Found on the palm side of fingers & hands, soles of feet and toes. ► Formation occurs during fetal development. Fingerprints do NOT change over a lifetime. Identical twins have different fingerprints! Fingerprints grow back when damaged. Three (3) Types of Fingerprints ► Latent Invisible fingerprints. Formed when sweat, oil, amino acids, & water are deposited in the formation of the ridge pattern. ► Plastic Impressed into soft materials. ►Gum, ► Visible wax, soap, dust, putty, etc… or Patent Fingerprint left in a visible material ►Ink, grease, blood, paint, etc… Fingerprint Composition ► Sweat Eccrine sweat glands ►Produce a “watery” sweat. Apocrine sweat glands ►Produce ► Proteins ► Lipids an “oily” sweat Skin Anatomy ► Epidermis Top Layer of Skin (2 mm in fingers) Contains keratin, melanin, & immune cells. ► Dermis Thick layer of connective tissue. Contains blood vessels, nerves, muscles, oil & sweat glands, & hair follicles. ► Papillae Boundary between layers; forms ridge pattern. Papillae Major Ridge Patterns ► Loops ► Whorls ► Arches LOOPS ► 60% of population. ► Two (2) or more ridges entering from one side, curving and exiting on the same side. Core ►Center of loop Type Lines ►Ridges that diverge Delta ►Closest ridges to type lines; forms a triangle. Anatomy of a Loop Types of Loops ► Radial Loop ► Ulnar Loop opens towards thumb. Loops Loop opens towards pinkie. WHORLS ► 30%-35% of population. ► Must have type lines and a minimum of two (2) deltas! ► Four types: Plain Whorl Center Pocket Whorl Double Loop Whorl Accidental Types of Whorls ► Plain Whorl ► Center Pocket Whorl Plain vs. Center Pocket Whorls ► Both have at least one ridge that makes a complete circuit. Draw a line through the deltas. Plain – hits the circuit ridge. Center Pocket line does NOT touch circuit ridge! Types of Whorls ► Double Loop Whorl ► Accidental ARCHES ► 5% of population. ► Simplest of all fingerprints! ► Ridges enter on one side of print and exit on the other. Slight or dramatic rise in the center. Plain Arch vs. Tented Arch ► No type lines or deltas. Types of Arches ► Plain Arch ► Tented Arch Fingerprint Analysis ► Used ► Not to match a suspect to a crime scene. based upon general shape or pattern. ► Requires ► Average a point by point match of minutiae. fingerprint has 150 minutiae. 8 to 16 matches adequate in court. No statistical studies regarding locations of common minutiae in populations. Minutiae ► Ridges – raised points on a print. ► Groves or Furrows – low points on a print. Minutiae (Ridge characteristics) ►Ridge Endings ►Short Ridge ►Bifurcation ►Island or Dot ►Enclosure (or Lake) ►Crossover Minutiae Mapping Comparing Minutiae Maps Latent Fingerprint Removal ► Depends upon: Type of surface ►Porous vs. Nonporous ►Soft vs. Hard How the print was left. ►Visible vs. Invisible (latent prints) Amount of print available. Latent Print Removal ► Dusting ► Superglue Fuming ► Amino Acid Reaction ► Iodine Fuming Dusting ► Surface: Smooth, nonporous. ► Chemical: Carbon black powder ► Method: Dust on powder with brush. Remove excess powder (puff of air). “Lift” print with tape. Place on index card. Superglue Fuming ► Surface: Smooth, nonporous. ► Chemical: Cyanoacrylate ► Method: Place print evidence in sealed container. Add few drops of superglue + heat. Takes 2-3 hours; chemical fumes stick to print. Amino Acid Reaction ► Surface: Porous. ► Chemical: Ninhydrin ► Method: Spray or dab chemical onto print area. Allow to dry (2-3 hours). Turns pink when it reacts with proteins. Highly effective on old prints (up to 15 years!) Iodine Fuming ► Surface: Porous. ► Chemical: Iodine crystals (solid) ► Method: Place print evidence in sealed container. Sublimation of iodine crystals. ►Solid to GAS! Vapors attach to print. Not permanent! Must photograph!