Since the identification of body fluids in evidentiary stains may provide investigators with probative information during an investigation, this study performed quantitative reverse transcription polymerase chain reaction (RT-qPCR) assays to detect the presence of mRNA and miRNA in fresh and environmentally challenged samples.
Blood, semen, and reference markers were chosen for both mRNA/miRNA testing. Samples of blood and semen were exposed to heat, humidity, and sunlight, and controlled conditions (room temperature, low humidity, and darkness) for 6 months. All mRNA targets were observed through 6 months under controlled conditions, but were undetected after 30 days in experimental conditions; however, miRNA targets persisted under all test conditions for the duration of the study. In addition, cotton stained with blood or semen was laundered using a liquid detergent in various washing and drying conditions. An unstained cutting was evaluated for potential transfer. Both miRNA targets were observed in all stained samples regardless of the wash protocol used. Of the mRNA markers, HBB was detected in all bloodstained samples and PRM1 persisted in all but one semen stained sample. The unstained samples showed transfer of at least one body fluid specific miRNA marker in all samples and at least one body fluid specific mRNA in approximately half of the samples. These results indicate that RNA markers can be used for body fluid identification in challenging samples, and that miRNA markers may be more persistent than mRNA for blood and semen stains; however, some caution is warranted with laundered items due to possible transfer.(publisher abstract modified)
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Date Published: May 1, 2019