Dating human skeletal remains using a radiometric method: Biogenic versus diagenetic 90Sr and 210Pb in vertebrae

In forensic science, there is a strong interest in determining the post-mortem interval (PMI) of human skeletal remains up to 50 years after death. Currently, there are no reliable methods to resolve PMI, the determination of which relies almost exclusively on the experience of the investigating expert. Here we measured 90Sr and 210Pb (210Po) incorporated into bones through a biogenic process as indicators of the time elapsed since death. We hypothesised that the activity of radionuclides incorporated into trabecular bone will more accurately match the activity in the environment and the food chain at the time of death than the activity in cortical bone because of a higher remodelling rate. We found that determining 90Sr can yield reliable PMI estimates as long as a calibration curve exists for 90Sr covering the studied area and the last 50 years. We also found that adding the activity of 210Po, a proxy for naturally occurring 210Pb incorporated through ingestion, to the 90Sr dating increases the reliability of the PMI value. Our results also show that trabecular bone is subject to both 90Sr and 210Po diagenesis. Accordingly, we used a solubility profile method to determine the biogenic radionuclide only, and we are proposing a new method of bone decontamination to be used prior to 90Sr and 210Pb dating.