Homicides and violent crimes often result in bloodshed; the constant substrate involved in physical altercations in the commission of violent crimes is human skin. Thus, it is likely blood impressions are left on the skin of living victims or decedents during these violent interactions. Yet, skin is one of the least studied substrates in the impression discipline. In some cases, impressions are clearly visible but, it is much more likely that they are latent and not readily visible. There have been cases where the enhancement of blood impression evidence on human skin was possible, but it is not standard practice, especially when blood impressions are latent. While visible blood impressions are best enhanced in situ at the scene of the crime, most often these impressions on decedents are not enhanced until the body is moved to the medical facility for autopsy increasing the possibility of damage to the impression evidence from handling and/or moving the body. Because it is semi-porous, skin is a difficult substrate to enhance through chemical enhancement methods due to background staining, which may result in suboptimal visualization of the impressions. In addition to the staining of skin, visualization of impression details may be obstructed by competing background patterns, such as dermal scales, hairs, wrinkles, and variations in skin tones. Two commonly used dye stains, Amido Black and Hungarian Red have been used to enhance blood impressions on human skin and a newer method, Zar-Pro™ Fluorescent Blood Lifters have also been used in preliminary studies to effectively lift and enhance blood impressions from decedent skin. A comparative analysis between methods conducted in collaboration with the Forensic Research Outdoor Station at Northern Michigan University assessed the effectiveness of enhancing semen smears and blood impressions on decedent skin during the early stages of decomposition. All three enhancement methods demonstrated effectiveness in recovering proteinaceous materials with Amido Black and Hungarian Red primarily effective as insitu dye stains. The dye-stained impressions were not reliably lifted using BVDA Gellifters® thus not removing the substrate variables that can impede visualization of impressions on skin. The ZarPro™ Fluorescent Lifters were able to effectively lift and fluorogenically enhance proteinaceous materials in the form of blood impressions and semen smears from decedent skin through ten days of active decomposition. A statistical assessment of the enhancement methods was conducted amongst examiners to verify the efficacy of results. During the early stages of decomposition, donor skin will deteriorate, thus recoverable impressions will also be degraded and or damaged, yet this degradation is not perilous for the recovery of proteinaceous materials as long as the epidermal skin is still intact. Thus, even during active decomposition, skin, arguably one of the most difficult substrates for impression recovery, can produce viable impressions and the recoverability of this vital evidence can now be re-evaluated by practitioners in the field.
(Author provided abstract.)