Determination of a Recharge Time for Eccrine Sweat Glands on Friction Ridge Skin

A single fingerprint can provide a great amount of information. Latent prints, in particular, can help tell a story or identify a perpetrator in criminal and civil cases. Even though fingerprints have been a valuable tool in the field of forensic science since the early 1900s, there is still much to learn about their nature and evidentiary value (National Institute of Justice, 2011). The purpose of this study is to explore the natural, or uncharged, fingerprint and determine what point, if any, it will appear the same as a groomed, or charged, fingerprint. This was carried out through the deposition of hundreds of prints at various time intervals on a porous substrate. After 5, 15, 30, and 60 minutes, an uncharged print was deposited onto plain white copy paper. It was then cut in half and processed by two different reagents: Ninhydrin and Oil Red O (ORO). These visualize the amino acids and lipids, respectively, which are commonly present in latent fingerprint residue found at crime scenes. After development, the prints were analyzed for color intensity and quality of ridge detail with the AATCC Gray Scale for Change and the Snaidauf Modified Bandey System, respectively. Results were documented and percentages, means, and standard deviations calculated for each time interval. Overall, there were no significant changes across all time intervals. In addition, uncharged prints developed with ORO behaved much differently than charged prints. A recharge, or recovery time, was unable to be determined for the eccrine sweat glands. At no point will an uncharged fingerprint appear the same as a charged fingerprint within the conditions of a laboratory setting.