Evaluation of fingerprint development reagents for biological stain detection
Banh, Hung Nghiep
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Some latent fingerprint development techniques rely on the reaction with amino acids within the fingerprint and then either change in color or fluoresce to help visualize this fingerprint. Amino acids are the building blocks of proteins and are present in all biological fluid. Thus, these developers should be able to also locate biological stains. In a previous study, ninhydrin was shown to be able to locate biological stains. Two more latent fingerprint developers are introduced as possible universal biological stain detectors: 1,8-diazafluoren-9-one (DFO), and 1,2-indanedione (1,2-IND). Five biological stains were used to test these chemicals: 1:500 diluted blood, saliva, semen, sweat, and urine. A new heating method was also introduced for a more portable application. The hair dryer heating method was optimized for the three chemicals with two traditional oven heating methods: the oven setting at 70oC and the oven setting at 100oC. These chemicals were also examined for their effectiveness on aged samples. Samples aged for three different time intervals were used: 4 weeks, 8 weeks, and 16 weeks. The hair dryer heating method was found to be viable for all three chemicals for each of the biological stains except the 1:500 diluted blood. With the application of the hair dryer for less than 3 minutes, most stains were visible for all three chemicals. 1,2-IND gave slightly different color changes for sweat and the other biological stains. This property can possibly be used to guide subsequent specific body fluids testing. All three chemicals lost their effectiveness as the stain became older. One-month-old stains still gave similar results as fresh stains, but after 2 months, the color became fainter and was barely visible after 4 months. The next stage of this study applied these chemicals as a guide for wearer DNA extraction from worn clothing. Sampling for wearer DNA has mostly been an educated guess with little guidance as to where an abundance of DNA is located. Fingerprint developers can react with amino acids, and cells contain abundant amino acids. Thus, these chemicals may react more to areas with abundant cells. Wearer DNA was extracted from collars of donated shirts before and after the chemical applications to determine the effectiveness of these chemicals as DNA detectors. Of the three collars tested, ninhydrin reacted completely with two of the collars, making any distinction between areas with abundant DNA and areas with no DNA difficult. In addition, the quantitation data of the ninhydrin samples showed no advantage in using ninhydrin as a wearer DNA locator. DFO was shown to have some detrimental effects on the DNA or the DNA extraction and quantitation process. The quantitation data for DFO also showed no advantage in using DFO as a wearer DNA locator. 1,2-IND showed promising results and was the most likely candidate as a wearer DNA locator. All areas that reacted with 1,2-IND produced at least one sample having higher than 0.01 nanograms per microliter of DNA and would be considered viable for DNA profiling.