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FINGERPRINTS Slide 2 Wednesday - 10/19/11 Objective: To describe the characteristics of fingerprints Do Now: Are fingerprints considered class or individual evidence? Today: Last H-option Presentation Fingerprinting Slide 3 Thursday 10/20/11 Objective: To describe the characteristics of fingerprints. Do Now: Read Unaltered Identity on p. 132 of text book. Answer question: Can fingerprints be altered? Explain. Today: Fingerprinting Notes Ten cards Slide 4 Slide 5 WHAT ARE FINGERPRINTS? -Hands, feet have unique pattern of skin ridges -Skin is coated with mix of sweat and oils -Any time you touch a surface, a trace amount of sweat/oil is left behind Slide 6 HOW DO THEY FORM? -Form on a fetus in the womb -The basal layer of skin grows faster than the epidermis and the dermis, making it wrinkle in random patterns -Twins do NOT have identical prints -Genetics does NOT determine your exact prints Slide 7 HISTORY 2000 BC: Ancient China & Babylonfingerprints on clay tablets and official documents (used for ID? We dont know.) 1788: Johann Mayer observes that fingerprints are unique to each person 1879: Alphonse Bertillon, clerk at a police records office in Paris, uses fingerprints to identify a repeat- offender criminal Slide 8 Types of Fingerprints Patent Prints : visible prints (left because someones hand had blood, ink, etc. on it) Latent Prints : hidden prints that become visible only when fingerprint powder or other special techniques are used. Composed of sweat and body oils. Plastic Prints : fingerprint indentations left in a soft material such as clay or wax Slide 9 WHAT TYPE IS THIS? A)Latent B)Plastic C)Patent Slide 10 WHAT TYPE IS THIS? A)Latent B)Plastic C)Patent Slide 11 WHAT TYPE IS THIS? A)Latent B)Plastic C)Patent Slide 12 WHAT TYPE IS THIS? A)Latent B)Plastic C)Patent Slide 13 AFTER DUSTING FOR PRINTS Slide 14 WHAT TYPE IS THIS? A)Latent B)Plastic C)Patent Slide 15 Reliability of Fingerprints UNIQUE: No two identical fingerprints have ever been found. Remain same for entire life. ALTERATION: Fingerprints grow back. (Story of John Dillinger, a famous gangster.) Scars dont cover the whole print. MISTAKES: Human error is the cause of fingerprint ID errors. (Case of Brandon Mayfield/Madrid bombing.) Slide 16 Characteristics of Fingerprints (Book pg 137 you need to see pictures!) Arches (5%) Plain and Tented Whorls (30%) Plain, Central pocket loop, double loop, accidental Loops (65%) Deltaa triangular region near a loop Corethe center of a loop or whorl PURPOSE: categories provide quick way to eliminate suspects. They DO NOT give an individualized identification of one person. Slide 17 PLAIN ARCH -No core -No delta -4% of population Slide 18 TENTED ARCH -No core -Presence of a DELTA is what makes it tented -1% of population Slide 19 PLAIN WHORL -Has core ridges go in complete circle around it -2 deltas; a line drawn between deltas will cut at least one of the circles around core -24% of population Slide 20 CENTRAL POCKET LOOP WHORL -Core has ridges in complete circle -2 deltas -Line between the deltas DOES NOT cross circles around core -2% of population Slide 21 DOUBLE LOOP WHORL -Contains 2 loops (so 2 cores) -2 deltas -4% of population Slide 22 ACCIDENT AL WHORL -Has 2 or more deltas -Combines 2 or more other patterns (loops, whorls, arches) but is not a tented arch -0.01% of population Slide 23 LOOP -Has core, but the core has no complete circles around it -1 delta -65% of population Slide 24 1) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 25 2) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 26 3) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 27 4) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 28 5) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 29 6) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 30 7) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 31 8) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 32 9) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 33 10) WHAT TYPE? -How many cores does it have, if any? -How many deltas does it have, if any? -Does a line between deltas cross core circles? Slide 34 RIDGE COUNT -Way to help individualize prints -Imagine a line from core to edge of delta -Count how many ridges are crossed Slide 35 MINUTI AE -This is where it gets real, folks! -Primary means of individualizing prints -Every print has about 150 minutiae -Need 8-15 for match (basis of computer matches) Slide 36 Comparison of Minutiae Slide 37 IAFIS Integrated Automatic Fingerprint Identification System (was AFIS before going international and is often still called AFIS) Computerized system that uses ridge counts and types/locations of minutiae to match fingerprints to the 50 million in the database Matches take hours, not seconds! Slide 38 Detection of Latent Prints Dusting with powders Spraying/applying ninhydrin Exposing to cyanoacrylate fumes (superglue) Spray or dip in silver nitrate Expose to iodine fumes Slide 39 DUSTING FOR PRINTS Fine dusts (often charcoal) stick to the sweat and oils on prints Works best on smooth, nonporous surfaces (plastic, smooth metal, polished wood, glass) Colored dusts provide better contrast depending on surface Excess dust blown away Fingerprint is then photographed Then lifted with tape and placed on a fingerprint collection card Slide 40 Dusting - disadvantages -Messy; prints can be smeared by brush (magnetic dust and magnetic dust remover helps in some situations; fluorescent dusts and UV lamps help) -Doesnt work on rough or porous surfaces (unfinished wood; paper; Styrofoam; leather) -Not as sensitive as other techniques (which means that some prints may be too faint to appear from dusting) Slide 41 Iodine fuming Gets prints from paper, cardboard, unpainted/unfinished wood (porous surfaces) Solid iodine is heated in a vapor tent, producing iodine vapors (sublimation) Iodine crystallizes on prints, forming a brownish color It fades quickly unless sprayed with a starch solution Not used much anymore more toxic, less sensitive than other methods Slide 42 Iodine fingerprint (photograph it or spray it with starch!) Slide 43 After Image Adjustment Slide 44 Cyanoacrylate (superglue) Gets prints that are on plastic, metal, or glass Item is placed in a vapor tent (enclosed area to contain fumes). Superglue is heated to create fumes. Can take hours. Reacts with amino acids & water and becomes a white solid (harder to see than other types) Slide 45 Slide 46 Ninhydrin Best for getting prints off of paper Paper is sprayed with a solution of ninhydrin in acetone or alcohol Ninhydrin reacts with amino acids (proteins) in sweat and becomes purple-blue Takes up to 24 hours for prints to appear; ninhydrin is toxic and flammable Slide 47 Silver nitrate Gets prints from paper, wood, Styrofoam (better at detecting faint prints than almost any other method) Object sprayed or dipped in AgNO 3 Chloride from salt in sweat reacts to become silver chloride (AgCl), a white compound Silver chloride is black or reddish-brown under UV light AgNO 3 + NaCl AgCl + NaNO 3 Permanently damages the materialused as a last resort if other methods fail