mRNA As A Forensic Target – A Bridge Too Far

Abstract
Individual human tissues are distinguished by distinctive RNA expression profiles, with the expression of many RNAs restricted to certain cell types only. Reverse transcription polymerase chain reaction (RT-PCR)-based assays are widely used in research and diagnostic applications to exploit this tissue-specificity for the identification of unique or aberrant cells. This feature has also led to an extensive evaluation of their potential to identify RNA transcripts that will reliably, sensitively and definitively identify tissues of origin in forensic casework applications. An analysis of the literature published by forensic scientists highlights a divergence of methodologies, protocols, reagents and interpretative models for forensic RNA studies. Disconcertingly, it also suggests the widespread application of protocols that are optimised for the analysis of DNA but are inappropriate for reliable RNA detection as well as the use of non-human and non-tissue-specific markers. Since the interpretation of RT-PCR-based results is dependent on the properties of the RNA as well as the variable characteristics of RT-PCR, this has serious consequences with regards to the robustness, consistency and reliability of any conclusions. A consensus on the most appropriate approach for reliable, accurate and meaningful RNA investigation as a forensic tool remains to be established.