Taphonomic study on drowned victims in a non-sequestered aquatic environment in the Mediterranean Sea

Human decomposition in sea water poses several challenges to forensic practitioners tasked with the analysis of drowned bodies. Postmortem changes in the marine environment have not been extensively investigated and the current literature is mainly based on bodies retrieved from shallow waters or on limited samples. On 18 April 2015, a fishing boat carrying allegedly 1,000 migrants sank in the Mediterranean Sea. In a fifteen-month time span, humanitarian missions were carried out to recover the bodies from the sea. The present study investigates postmortem changes on the drowned victims in a non-sequestered environment in the Mediterranean Sea. A retrospective study was performed by two observers on the autopsy photographic records in the series of bodies recovered from the open sea. For 184 bodies, the postmortem changes were evaluated according to facial, body, limb, and total aquatic decomposition score (FADS, BADS, LADS, TADS, respectively). Furthermore, a modification to the current scoring system that divides upper and lower limbs was suggested. The interobserver agreement was assessed using Krippendorff's alpha coefficient. Possible relations between the decomposition scores and PMSI were investigated with Pearson correlation analysis. According to the sequence of the recovery missions, increasing FADS, BADS, LADS, and TADS were observed. The modified scoring system showed a strong agreement between observers, allowing a more accurate description of the actual extent of decomposition. The scores showed a significant relation with the PMSI (p < 0.01). Prolonged submersion in the open marine environment was confirmed to show increasing decomposition rates, from moderate decay to full disarticulation. This study provides a descriptive unicum of the postmortem changes in the open sea, which may contribute to strengthen the discipline and aid description of bodies recovered in similar circumstances, especially if a body needs to be associated to a disaster or period with respect to another, thus facilitating families or authorities in the search for specific victims.