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Advances in Fingerprint Technology.pdf

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4. R<strong>in</strong>se the specimen <strong>in</strong> tap water.<br />

5. Dry the specimen thoroughly with a temperature-adjustable hair dryer.<br />

6. Reprocess weakly developed latent pr<strong>in</strong>ts (low contrast) <strong>in</strong> PD work<strong>in</strong>g<br />

solution.<br />

7. Photograph the developed latent pr<strong>in</strong>t(s).<br />

8. The visualization of latent pr<strong>in</strong>ts developed on soiled and darkened<br />

surfaces can be enhanced by immers<strong>in</strong>g the specimen <strong>in</strong> a 50% dilution<br />

of common household bleach.<br />

Margot and Lennard 9 describe recipes for the orig<strong>in</strong>al reagent mixtures<br />

and the Phillips, Cole, and Jones modification 159 just given. In addition, they<br />

mention a simplified PD, personally communicated to them by Saunders <strong>in</strong><br />

1993 and fully described <strong>in</strong> Chapter 7 of this volume. The Phillips, Cole, and<br />

Jones physical developer described above is more stable and produces better<br />

pr<strong>in</strong>ts than the Saunders recipe.<br />

Modified Physical Developer Methods<br />

In 1989, Saunders and the U.S. Secret Service Forensic Services Division<br />

reported a new procedure <strong>in</strong>volv<strong>in</strong>g the use of colloidal gold with PD. This<br />

technique was called “multimetal deposition” (MMD). 160 An additional colloidal<br />

gold step was used. Collodial gold at pH 3 b<strong>in</strong>ds to am<strong>in</strong>o acids,<br />

peptides, and prote<strong>in</strong>s <strong>in</strong> f<strong>in</strong>gerpr<strong>in</strong>t residue. The bound colloidal gold provides<br />

a nucleation site around which silver precipitates <strong>in</strong> the second <strong>in</strong>cubation<br />

step. The follow<strong>in</strong>g is the procedure for the multimetal deposition<br />

method:<br />

Reagents<br />

Stabilized Physical Developer: Colloidal Gold<br />

Solution A: Redox<br />

Ferric nitrate 33 g<br />

Ferrous ammonium sulfate 89 g<br />

Citric acid 22 g<br />

Tween 20 1 mL<br />

Distilled water 1 L<br />

Notes: Dissolve the chemicals <strong>in</strong> the order listed <strong>in</strong> 1 L distilled water and then add<br />

the Tween 20. This solution is stable <strong>in</strong>def<strong>in</strong>itely at room temperature.<br />

Solution B: Silver nitrate<br />

Silver nitrate 20 g<br />

Distilled water 100 mL

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