Comparison of Oil Red O vs Physical Developer enhancement of latent prints under various environmental conditions
Burke, Erin M.
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For the past several decades, latent prints have served as a valuable source of evidence in the forensic field. They have proved capable of linking victim(s) and suspect(s) to crime scenes. Despite their value, latent print evidence is extremely sensitive to the exposure of various environmental conditions. This exposure has presented challenges in their detection and collection. The constituents that make up a latent print are comprised of lipids, fats and amino acids found in sweat. Depending on the surface upon which the print was deposited, a specialized enhancement technique will be used to visualize the prints. This study sought to compare two latent print staining techniques, Oil Red O (ORO) and Physical Developer (PD), on various porous substrates including cardboard, thermal paper receipts, masking tape, standard printer paper and brown kraft paper. Each substrate was tested under different environmental conditions including exposure to room temperature, moisture and high humidity conditions. Additionally, an aging study was conducted at 3 weeks and 4 weeks for latent prints on thermal paper. To determine which enhancement technique yielded stronger results, a comparison of ridge detail was conducted. Each latent print was photographed and digitally processed using Adobe Photoshop in accordance with Worcester Police Department’s (WPD) standard operating procedures. Results demonstrated that thermal paper receipts and standard printer paper were among the most successful substrates for latent print recovery. Further, ORO outperformed PD in almost in every environmental condition apart from wet thermal paper. ORO treated prints that were aged 4 weeks demonstrated sufficient friction ridge detail. These results indicate that ORO is a useful enhancement technique for latent prints, and may be suitable as a replacement for PD.