Recommendations for identifying disaster victims from the “Mass Grave Project”: forensic genetics issues

Disaster victim identification poses serious challenges to forensic scientists, including bodies or body parts requiring identification in remote places with limited laboratory access. In these settings, samples for genetic analysis may be collected at a later, after freezing of the corpse. Therefore, given the ease of collection and the possibility of preservation under harsh conditions, swabs can be a viable alternative to tissue and bone sampling. As DNA yield varies by anatomical region, maximum DNA recovery and sampling as many tissues as possible are important to maximize the success of the analysis. As part of the Mass Grave Project, an interdisciplinary taphonomic study simulating primary and secondary clandestine mass and single graves with whole body donors at the outdoor research facility of the Forensic Anthropology Center, Texas State University (FACTS), nine body donors were examined with the aim of proposing sampling strategies and recommendations for the human identification through DNA analysis. Swabs were collected upon arrival of donors at FACTS and after freezing (between 12-455 days). The donors were then buried for 18 months, six in a mass grave and three in single graves. After burial, biological material in the form of swabs (skin, oral, rectal, periocular) and tissues (muscle, nails, internal organs, cartilage) was sampled. The inter/intra-individual variation in DNA quantity and quality was explored through STR typing. The results show a progressive loss of information within defrosted and decomposed bodies, unaffected by the observed degree of decomposition of the tissues nor by the position of the body within the mass grave. Our analyses show that freezing and burial can affect personal identification, so it is good practice to sample as many biological tissues/fluids as possible even considering 'uncommon' sampling such as rectal swabs, and proceeding as quickly as possible to successfully identify the remains of unknown individuals.