Comparison of chemiluminescent and fluorescent blood detection kits
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Blood at a crime scene is not always detected by the naked eye, and hence requires the use of special reagents and alternate light sources. Two of these reagents – luminol and fluorescein – have been in use in forensic science both in their original forms and in the form of commercially produced reagents, Bluestar® and Hemascein™. The manufacturer of Hemascein™, the relatively newer product, states that the reagent exhibits lower amounts of cross-reactivity with bleach and is less detrimental to DNA as compared to Bluestar®. They also say that the reagent does not require complete darkness to function, unlike Bluestar®. These parameters, along with the impact of Bluestar® and Hemascein™ on pattern detail, were evaluated in this study. It was found that both reagents exhibited some positive reactions with bleach; however, Bluestar® had a less intense reaction with lower concentrations of bleach, while Hemascein™ showed a lower intensity for cross reactions with higher concentrations. A distinct difference was observed for the reagents with respect to retention of pattern characteristics in bloodstains, with Hemascein™ causing considerable diffusion of the pattern. The results also demonstrated that there was a dependence of the color of the substrate on the performance of Hemascein™, with lighter colored substrates far outperforming their darker counterparts. Hemascein™ performed better than Bluestar® in well-lit conditions, with a positive luminescent reaction observed in ambient lighting conditions. Additionally, neither of the reagents showed inhibition during quantitative PCR, thus deeming them both appropriate for use when subsequent recovery of DNA is desired. There were differences in the amounts of DNA recovered from the treated blood samples, however, further studies and a larger sample size would be required to determine if these variations are related to the application of Bluestar® and Hemascein™. All DNA recovered was sufficient in quantity to expect successful DNA profiling if such analysis had been carried out.