This study investigated whether the age of biological evidence (dried blood samples) could be determined by changes in two types of RNA molecules.
The results indicated that the two types of RNA (mRNA and rRNA) changed over the course of a 150-day period in a linear fashion. Although rRNA was found to decay more rapidly than mRNA, both types were found in abundance, leading to the conclusion that only a small sample size was required to conduct the analysis. Estimates can also be made over a relatively broad range of time and the techniques required to perform the analysis are similar to the DNA PCR techniques currently in widespread use. Another advantage to this method is that probes can be made species-specific, eliminating the possibility of false data from other sources. Research methods involved the extraction of blood from four males and four females of European decent, which were then placed on pieces of 100 percent cotton fabric and stored at 25 degrees C and 50 percent humidity. RNA was isolated using TRI Reagent BD. DNA was also extracted from the same bloodstain. Analysis techniques included reverse transcription, real-time PCR, relative RNA quantification, and RiboGreen quantification of RNA. Bloodstains were analyzed at day 0, day 30, day 60, day 90, day 120, and day 150. Statistical analysis involved the use of nested analysis of variance. Research is ongoing on the effects of environmental factors, such as microorganisms, temperature, and humidity, on RNA decay. Figures, tables, references
Date Published: January 1, 2005