Transcript WARM UP 1/7
WARM UP #4 1. 2. 3. 4. 5. What percent of people have arches? What did Galton do? What are 5 different ridge characteristics we learned last class? What is the science names of the ridges on our fingers that make our prints? How many ridge patterns need to be shown to hold up in court? A preoccupation among criminals in the past has been to eradicate their own fingerprint impressions. The use of gloves and wiping objects they had touched at the crime scene were obvious precautions, but in two famous cases more drastic measures were taken. The American gangster John Dillinger had his fingertips treated with acid in the 1930s to remove the ridge patterns, and Robert Phillips, another American criminal, had the skin on the fingertips removed by plastic surgery and replaced with skin grafts taken from his chest. Both attempts failed miserably. Dillinger's ridge patterns reappeared, and Phillips was identified by impressions taken from the undoctored second phalanges of his fingers. Such painful methods of eliminating fingerprints quickly went out of fashion, and criminals resorted to the use of gloves, although glove prints, especially of leather or woven gloves, opened up new vistas for the detective with prints from gloves and now DNA samples from inside gloves. NOTES CH 6 #3 5/29 In solving crimes, must compare prints found at the crime scene with prints on file. FBI – created a database called the AFIS. All criminals arrested anywhere in the world get fingerprints added to file. (Or anyone having prints taken) * Has 450,000,000 prints on database * ABOUT 40,000 prints added daily! If the person was never fingerprinted, you will only be able to compare if you have a suspect. TECHNIQUES TO LIFT FINGERPRINTS 1. DUSTING * for smooth surfaces (glass, painted, coated) * most common and oldest technique • • • • Power brushed over print Sticks to oils left behind Photograph Lift using tape and placing on a print card Fluorescent and phosphorescent fingerprint powders have been created see prints better on colored or clear surfaces 2. IODINE FUMING * for paper, cardboard, wood • • • • Object placed in container with iodine crystals and heated Iodine sticks to oils left behind and turn it brownish Only temporary (need to photograph it) Spraying with starch solution will make it last longer (bluish color) 3. Superglue fuming (cyanoacrylate) * used for plastics ( bags, tape, rubber, cellophane, etc.) • Object placed in jar with superglue Chemical sticks to oils in print Turns white • • 4. NINHYDRIN * Most common for paper • • • Chemical sprayed on Chemical sticks to amino acids in prints In about an hour (or faster if heated) prints will appear purple 5. SILVER NITRATE * good for paper and cloth • • Reacts with salts in print Done last since it washes away a.a and oils 6. GENETIAN VIOLET • • Pour dye over print Stains epidermal cells or salts from print Impressions on skin may also be seen using special X-ray techniques. Advanced techniques are also being applied to the location of latent fingerprints at the crime scene, such as fluorescence under laser illumination. 7. Gelatin tape For smooth surfaces Picks up print 8. X-rays Good for human skin and difficult substances,( like paper, wood, leather) Reacts with sweat Little or no damage to print Can photograph it