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Crime Scene Fingerprints

“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)

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Crime Scene Fingerprints

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  1. “Regrets are as personal as fingerprints.” - Margaret C. Banning Crime Scene Fingerprints

  2. 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 What types can you leave?

  3. Visible prints

  4. Plastic prints

  5. Latent prints

  6. 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

  7. 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 Fingerprint powders

  8. 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 Iodine fuming

  9. 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! While we are fuming…

  10. 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 What about porous surfaces?

  11. 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 Physical developer (yes, that’s its name…)

  12. 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 After all this, we want to preserve them!

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