| Plastic items can be difficult to process for latent prints using black powder as the prints become engulfed in powder and any fingerprint ridge detail can be lost. In the research presented, over 100 plastic items and nearly 300 fingerprints were tested to examine what plastic characteristics result in an enhanced print when the powdered print was washed with a ninhydrin hexane solution. Features such as plastic type, inked printing, presence or absence of labels, color, surface finish, surface tension, and surface roughness were analyzed to evaluate their influence on the rinsing method success. Microscopic examinations were made using Scanning Electron Microscopy to identify the changes that occurred to the print between the cycles of powdering and rinsing. Scanning Electron Microscopy---Energy Dispersive X-Ray Spectrometry was used to examine the chemical interactions among the plastic, cyanoacrylate, black powder, and rinsing solution. High-density polyethylene plastic containers and bags demonstrated a strong success in enhancing latent prints after becoming engulfed in black powder. Rough textured surfaces tended to benefit from the rinsing solution. Inked surfaces typically had a lower success rate than those surfaces with a label or where a label had been removed. Results show that the powder/rinsing technique can act as another layer of latent print processing when other methods of enhancement have failed or powdering has obscured a print. |
