Experimental Formation of Marine Abrasion on Bone and the Forensic Postmortem Submergence Interval

Abstract

Human skeletal remains are frequently recovered from marine environments, where they have undergone months or years of immersion, and decomposition stage is no longer a possible method from which to estimate the postmortem submergence interval (PMSI). Over these longer PMSIs, a common taphonomic alteration that forms is the wearing and rounding of surfaces from marine abrasion, caused by repeated agitation in sediment or against rocks. Little is known about the timing of these changes and how to measure or score the degree of alteration. In a laboratory setting, multiple dry, defleshed bones of white-tailed deer (Odocoileus virginianus) were agitated in saltwater for varying intervals with abrasive sediment (1, 2, 4, 6, 8, and 10 days) and with rocks (5 and 12 days) using a laboratory tumbling device. These were compared to human remains cases from the Office of the Chief Medical Examiner, Boston, MA that had been in the Atlantic Ocean for known intervals. A five-stage (0–4) marine abrasion scoring system was devised for the taphonomic analysis of forensic cases from marine environments to allow for direct comparison among cases. A high degree of correlation between abrasion stage and known PMSI was detected.