crime scene fingerprints

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CRIME SCENE FINGERPRINTS “Regrets are as personal as fingerprints.” - Margaret C. Banning

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“Regrets are as personal as fingerprints.” - Margaret C. Banning. Crime Scene Fingerprints. v isible prints r idges in contact with a colored material b lood, paint, grease, ink p lastic prints r idge impressions left on soft material p utty, wax, soap, dust l atent prints (invisible) - PowerPoint PPT Presentation

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Page 1: Crime Scene Fingerprints

CRIME SCENE FINGERPRINTS

“Regrets are as personal as fingerprints.”- Margaret C. Banning

Page 2: Crime Scene Fingerprints

WHAT TYPES CAN YOU LEAVE? visible prints

ridges in contact with a colored material blood, paint, grease, ink

plastic prints ridge impressions left on soft material

putty, wax, soap, dust

latent prints (invisible) ridge impressions left by oils and perspiration

Page 3: Crime Scene Fingerprints

VISIBLE PRINTS

Page 4: Crime Scene Fingerprints

PLASTIC PRINTS

Page 5: Crime Scene Fingerprints

LATENT PRINTS

Page 6: Crime Scene Fingerprints

LOCATING AND DEVELOPING PRINTS The type of surface

determines how to make them visible hard, nonabsorbent

surfaces (glass, mirror, tile, painted wood)

soft, porous surfaces (papers, cardboard, cloth)

Most difficult aspect may be just locating the prints

Latest technology – RUVIS (reflected UV imaging system)

Can locate prints on nonabsorbent material without aid of powders or chemicals

Page 7: Crime Scene Fingerprints

FINGERPRINT POWDERS work best on nonabsorbent surfaces variety of composition and colors when applied lightly with camel-hair or fiberglass

brush, will adhere to residue of sweat and/or oils left on surface

choose color that contrasts with background best magnetic powder (less chance that print will become

damaged or destroyed) – useful on surfaces like leather or rough plastics (textures could hold onto too much regular powder)

fluorescent powders used to obscure backgrounds

Page 8: Crime Scene Fingerprints

IODINE FUMING solid crystal that sublimates iodine vapors combine with oils (or may

interact with residual water left on a print)

not permanent, begin to fade once fuming is stopped – should photograph ASAP

Page 9: Crime Scene Fingerprints

WHILE WE ARE FUMING… Superglue (cyanoacrylate) fuming as

well Fumes adhere to patent print, usually

producing a white pattern – still only on nonporous surfaces

Can use any small, enclosed area – even a car’s interior!

(movie scenes)

Page 10: Crime Scene Fingerprints

WHAT ABOUT POROUS SURFACES? ninhydrin – (triketohydrindene hydrate)

usually sprayed onto surface with aerosol can reacts with amino acids in perspiration solution prepared by mixing with solvent like

acetone or ethanol (0.6% solution is most effective)

prints begin to appear within an hour or two – can be sped up if treated in oven or hotplate

has developed latent prints on paper as old as 15 years

Page 11: Crime Scene Fingerprints

PHYSICAL DEVELOPER (YES, THAT’S ITS NAME…)

silver nitrate based liquid reagent detects prints that iodine and ninhydrin

may have missed also effective on porous surfaces that may

have been wet at one time application will wash away any traces of

proteins from an object's surface protocol – iodine first, then ninhydrin,

then PD

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AFTER ALL THIS, WE WANT TO PRESERVE THEM!

digital imaging picture converted into pixels, can be

enlarged for analysis photographs fingerprint tape

lifting print off surface, can be transferred to card for later study/scanning