An investigation into the performance of the ParaDNA® systems body fluid ID test on semen samples
Paradis, Kaylee Taylor
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Recent research efforts in the field of forensic biology include development of a confirmatory one-step testing methodology for biological fluids. Such techniques that have been shown to be promising include the analysis of deoxyribonucleic acid (DNA) or messenger ribonucleic acid (mRNA) contained within the specialized cells of specific body fluids. In current forensic practice, the possible biological origin of an evidentiary item or stain is often evaluated using protein-based presumptive testing. Ribonucleic acid (RNA) is an effective marker for the identification of body fluids because it codes for those specific proteins within the particular cells that make up each fluid. LGC has developed the ParaDNA® Body Fluid ID test that detects specific RNA markers allowing discrimination of six different body fluids. This research focuses on PRM2 and SEMG1, indicative of spermatozoa and seminal fluid, respectively. The ParaDNA® Body Fluid ID test was investigated to evaluate its performance with forensic semen samples and to determine if it is advantageous over current conventional semen screening methodology. Factors such as sensitivity, PRM2 and SEMG1 stability in aged stains at room temperature and in semen subjected to multiple freeze-thaw cycles, and performance on post-coital swabs were evaluated. Both spermatozoa and seminal fluid were detected in one of six 1:10 diluted stains tested and zero of six 1:50 diluted stains. Conventional semen screening methodology detected both components in six trials of 1:10 and 1:50 stains. PRM2 and SEMG1 were detected in stains prepared with neat liquid semen subjected up to 10 freeze-thaw cycles, in room temperature stains stored for up to 101 days, as well as in three different post-coital swabs. Of the 82 samples run on the instrument, 22 were false negatives, with a majority of them occurring during the sensitivity study with diluted stains, indicating the ParaDNA® Body Fluid ID Test is not yet suitable to replace current conventional screening methods. Upon further validation it could serve as a valuable tool for forensic laboratories.