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Analogs That React with Blood

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Where it is suspected there may be latent fingerprints in blood, and those prints may not be clearly visible, chemical techniques may be applied to enhance the appearance of fingerprints. Proper safety and care must be exercised when using the following techniques. The analogs are best used in aerosol form. This means that masks and gloves should be worn to protect the user against unnecessary contamination.

Coomassie Blue

When sprayed on the suspected area, the prints will turn dark bluish-black. Leucocrystal Violet

Per Medtech Forensics, Leucocrystal Violet is commonly used to enhance bloodstained fingerprints and footwear impressions. Leucocrystal Violet will not enhance a print composed solely of normal latent print residues,

Sticky side technique

Figure 5.48 Sticky side technique.

Sticky side technique

Figure 5.49 Sticky side technique.

Sticky side technique

Figure 5.50 Sticky side technique.

so it is used only in cases with blood-contaminated impressions. LCV is nearly colorless when first mixed, but is oxidized by the catalytic action of hemoglobin in the bloodstain, and will convert to a blue-colored solution, which will then stain the bloodstain. Premixed Leucocrystal Violet solution is an aqueous mixture containing Plydrogen Peroxide in addition to other chemicals. Always use in a fume hood or with other adequate ventilation and wear protective gloves and eyewear. Leucocrystal Violet can stain clothing and skin, so be careful. Read and follow the MSDS sheet.

Sudan Black

Per Arrowhead Forensic, Sudan Black is a dye that stains the fatty components of sebaceous sweat to produce a blue-black image. While Sudan Black is less sensitive than some other latent print development techniques, it is particularly useful on surfaces contaminated with grease, food residue, or dried soft drink deposits. It is also quite useful as a dye stain for cyanoacrylate developed prints. Sudan Black may be used on nonporous surfaces such as glass, metal, and plastics particularly if these surfaces are contaminated with greasy or oily materials. Sudan Black is not suitable for use on porous surfaces like paper, cardboard, or raw wood. Its principal advantages are its relatively inexpensive cost and its effectiveness on surfaces so badly contaminated that powders are inappropriate.

Rinsing tape agitating in distilled water

Figure 5.51 Rinsing tape agitating in distilled water.

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