This third episode of the 2019 R&D season of the National Institute of Justice's (NIJ's) Just Science podcast series consists of an interview with Dr. Robert Allen, professor and head of the Forensic Sciences Department at Oklahoma State University, who discusses a method for estimating the age of bloodstains using quantitative PCR.
Introductory information notes that RNA has been used to identify types of cells and to determine whether a blood sample came from two sources. Dr. Allen indicates that his team has found a new use for the single-strand genetic material, i.e., estimating the age of dried blood. By studying the ratios of degradation that occur in RNA, Dr. Allen's team was able to estimate the age of a bloodstain up to 3 years after the blood was deposited. The team focused on the link between the features of RNA degradation at various time points after blood was deposited. The team found that the link between time frames and degradation properties of RNA was dependable for up to 3 years, thus permitting an estimation of the time when blood at a crime scene was deposited for up to 3 years..