Assessment of RNA Stability for Age Determination of Body Fluid Stains

Time of deposition of a biological stain can be of value to determine the relevance of a sample in a forensic investigation. We assessed the possibility of using RNA transcript detection by duplex real-time PCR (RT-qPCR) to determine the age of body fluid stains commonly encountered in forensic biology. Targets included the ribosomal 18S RNA and the human β-actin, GAPDH and cyclophilin A mRNAs. Our results obtained from samples stored over a six month interval showed that the rate of RNA decay is similar for all markers tested in each type of tissue. For blood and semen, RNA degradation profiles of each target are correlated with time of storage. Moreover, the degradation rate of each target differs depending on the nature of the stain. In our study, decay rates of rRNA vs. mRNA targets did not exhibit significant differences, we suggest, however, that the degradation profiles of individual RNA markers may be useful to estimate the age of a sample as an exclusionary test. To our knowledge, this is the first study to investigate RNA stability in dried blood, semen, and saliva stains concurrently for age determination. We also assessed the impact of freezing biological stains at—80°C to determine if subsequent analysis would result in the loss of relevant information.