Abstract
Body fluid identification from crime scene evidence is crucial to determine the type of crime and to verify the victim’s testimony. We previously developed the multiple body fluid-targeted multiplex RT-PCR assay (MM) for simultaneous discrimination of blood, saliva, semen, vaginal fluid and nasal secretion. That procedure enabled precise and comprehensive identification of forensically relevant body fluids, especially in unknown or mixed biological samples. Alternatively, it is possible to narrow down the body fluid type by creating a case summary and performing a presumptive test for the expected body fluid and followed by a confirmatory test. In the present study, single body fluid-targeted multiplex RT-PCR assays (SM) were developed for the individual identification of blood, saliva, semen, or vaginal fluids. The repeatability of SM results was evaluated by using the pooled cDNA of each targeted body fluid and comparing it with the results of MM. Then, the peak height and detectability of each marker were compared between MM and SM on individual mixed and unmixed body-fluid stains. Like MM, the normalized values of SM were well reproduced in repeated electrophoreses. The positivity of the body-fluid markers was also well reproduced in repeated PCR amplifications. The average peak heights of some markers were significantly higher in SM than in MM. The detectability of SPTB, MUC7, and SERPINB13, which showed lower average peak heights among body fluid markers, was improved in SM. Comparable positive detection of other markers that showed sufficient amplification was found in SM and MM. The identification of targeted body fluid was performed based on the criteria we previously proposed, showing highly specific results. In conclusion, SM and MM can be performed individually or simultaneously based on the sample condition or case summary in order to precisely identify body fluid samples in forensic laboratories.
