The use of mRNA for the identification of body fluids is of particular interest in forensic science, and increasing support has been demonstrated for the use of microRNA (miRNA) analysis. MiRNA is more stable than mRNA and has been shown to be differentially expressed in body fluids. No studies involving miRNA analysis from previously extracted DNA samples have yet been reported. The aim of this experiment was to determine if it was possible to conduct miRNA analysis on samples that were previously extracted using standard DNA extraction. Blood and saliva samples were extracted using DNA and RNA kits, followed by cDNA synthesis, and then underwent quantitative PCR analysis. A direct comparison of ΔCt values shows a larger abundance of miRNA following DNA extraction as opposed to total RNA extraction for both blood- and saliva-specific markers. By carrying out a comparison between the amounts of said markers, it could be seen that the expression of the blood-specific marker was higher in blood than in saliva, and vice versa for the saliva-specific marker. The results obtained could have a profound impact on cases for which the sample has already undergone DNA extraction, such as in cold cases.
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