Abstract:
Latent bloodstains are valuable evidence at a crime scene. Leucocrystal Violet (LCV), the reduced form of Gentian Violet, detects bloodstains not easily visible to the naked eye on porous and non-porous surfaces and enhances the contrast of bloodstains for photography by producing a deep violet color upon reacting with the heme group in blood. Often, attempts are made to clean up crime scenes prior to their discovery. Commonly used household cleansers include bleach and bleach-based cleansers, abrasives, and enzymatic cleansers. The purpose of this research was to determine the reactivity of LCV with various common household cleaning products and to determine if LCV still reacted to blood that had been “cleaned up” using the cleansers at various strengths on various substrates. In total, 33 cleansers and five substrates were used. Each cleanser was first tested with LCV to determine if the cleanser produced a false reaction with LCV. A true positive reaction is one that shows a color change with the detection of blood when the substrate is developed with the LCV. If a false positive was found, a timeelapsed test was performed to determine the amount of time that must pass before the false positive was negated; LCV was not applied to a “cleaned” bloodstain until after that time period. For each cleanser evaluated, 0.25 ml of defibrinated sheep’s blood was deposited onto and evenly spread in a two-inch circular stenciled pattern on five different substrate materials: linoleum, laminated wood flooring, porcelain tile, painted dry wall, and painted wooden baseboard. The blood was allowed to dry completely. The blood was then cleaned using one of the cleaning products at the specified strength: 100%, 75%, 50%, and 25%. Ultrapure reverse osmosis water was used to dilute the cleansers. Each test was photographed to document results. Quality control tests were done each day using a 1/100th dilution of defibrinated sheep blood. Two cleansers, Great Value All Purpose Cleanser with Bleach and Clorox Bleach, did give a false positive result that dissipated after 30 minutes and 60 minutes, respectively, on all tested substrates. The results of this study showed that for all substrates and strength levels, 5.15% of cleaners showed presumptive negative reaction with the LCV. The results show that for all substrates and strength levels, 18.64% of cleaners had no effect on cleaning the blood off of the substrate. The results also show that the substrate that is best examined when looking for latent bloodstains is wooden baseboard.
