Effects of heat and burning on testing methods for blood and semen
Valenzuela Castillo, Maribel Beatriz
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Perpetrators of crime may sometimes attempt to destroy links that connect them to the crime scene. Limited information is known about the appearance and behavior of blood or semen stains collected from fire scenes. The purpose of this study is to observe the effects of high temperatures and flame exposure on blood and semen stains using current traditional presumptive (phenolphthalein, AP Spot test and ALS fluorescence) and confirmatory (ABAcard® Hematrace®, microscopic identification of spermatozoa and RSIDTM-Semen) testing methods. Liquid blood and semen was applied to swatches of denim, synthetic leather and carpet, and allowed to dry. In Part I of this study, the stains were exposed for various amounts of time to 130°C, 150°C, 170°C and 190°C using a laboratory oven. When bloodstains were exposed to high temperatures, reaction times using phenolphthalein increased and only bloodstains on denim were undetected within one minute at the most extreme conditions. Scraping was determined to be a better collection method than swabbing to test samples exposed to higher temperatures, and some samples required longer than the typical 10-15 second time frame used by most forensic labs to yield a positive reaction. Detection of human hemoglobin using ABAcard® Hematrace® was not possible after 1 hour at 130°C, making it a less sensitive test for bloodstains exposed to high temperatures than phenolphthalein. Semen stains exhibited fluorescence using an alternate light source after limited exposure to all temperatures, but more successfully on denim and synthetic leather than on carpet. AP Spot test was successful on all semen stains on synthetic leather, and on a number of samples on denim and carpet. Microscopic identification of sperm was most successful on denim but became impossible at higher temperatures and exposure times. Semenogelin testing was most successful on carpet and could be detected even under the most extreme conditions. Additionally, as temperature increased, semen stains darkened in color and appeared visually similar to bloodstains. [TRUNCATED]
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