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

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Presentation on theme: "“Regrets are as personal as fingerprints.” - Margaret C. Banning."— Presentation transcript:

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

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

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6  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

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

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!

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

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

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14  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


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