Effects of chemical blood enhancement methods on downstream biological testing
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Citation
Abstract
A common body fluid recovered from crime scenes is blood. The identification of bloodstains is important to forensic investigations as blood contains deoxyribonucleic acid (DNA), which can be used to generate genetic profiles for inclusion and exclusion comparisons of persons involved in a criminal investigation. Downstream testing of blood is also useful for forensic practitioners as it can identify human blood, which can be used for crime scene reconstructions, as well as for establishing potential linkages between the evidence, suspect, and/or victim. However, blood identification at a crime scene may not always be straightforward as the bloodstains remaining may consist of trace amounts or be non-visible (latent) if the suspect attempted to clean the area. As a result, forensic investigators may have to use chemical enhancement methods to locate potential bloodstains or to enhance bloodstains otherwise not visible. This study explored the potential effects chemical blood enhancements may have on downstream biological testing. Results concluded the Leuco Crystal Violet (LCV) chemical blood enhancement increased the number of false negative and inconclusive results when bloodstains were subsequently tested with the Kastle-Meyer and ortho-tolidine presumptive catalytic color tests as well as the ABAcard® HemaTrace® confirmatory immunoassay card. This was true for stains on both porous and non-porous substrates regardless of bloodstain size or time between enhancement application and subsequent testing. Results further showed the Grodsky luminol chemical blood enhancement reduced the number of positive results of diluted bloodstains when tested with the Kastle-Meyer presumptive blood test and correlated with a reduction in accurate detection of bloodstains when tested at 2 weeks or 2 months post enhancement with Ortho-Tolidine, Kastle-Meyer, and ABAcard® HemaTrace® on non-porous substrates. The Weber luminol chemical blood enhancement had the least effect on downstream biological tests, however, a reduction in positive detections were observed at 2 months post enhancement for the Kastle-Meyer and ABAcard® HemaTrace® blood tests on porous substrates.
Description
2024