DNA analysis of skeletal tissue recovered from the English Channel

Dead migrants in the Mediterranean: genetic analysis of bone samples exposed to seawater

In April 2015, a fishing boat that departed from Libya with about 1,000 migrants on board sank in the Mediterranean Sea. Most of the migrants were packed in the hull of the boat and drowned in the shipwreck. After fifteen months, the ship was recovered from the seabed and brought to a Sicilian naval area for forensic investigations. Skeletal remains belonging to more than 700 people were retrieved. A selected sample composed of 80 victims was considered in order to evaluate the possibility of achieving genetic profiles useful for a positive identification from these challenging specimens. The molecular features of the DNA recovered from a significant number of real casework samples exposed to seawater for long periods of time were described for the first time. Three different DNA extraction protocols and three different commercial kits were employed in order to generate genetic profiles based on the characterization of 21 autosomal STR loci. The combination of multiple DNA extractions and the cross-checking of multiple PCR amplifications with different kits allowed to obtain reliable genetic profiles characterized by at least 16 STR markers in more than 70% of the samples. The factors that could have affected the different quality of the genetic profiles were investigated and the bone preservation was examined through microscopic and macroscopic analyses. The approach presented in this study could be useful in the management of the genetic analysis of bone samples collected in other similar DVI scenarios. The genetic profiles recovered from the bone samples will be compared in kinship analysis to putative relatives of the victims collected in Africa in order to obtain positive identifications.

Development of a quantitative PCR-based method for studying temporal DNA degradation in waterlogged bone

While several studies have examined temporal DNA degradation in bones collected from terrestrial environments, studies on temporal DNA degradation in bones collected from aquatic environments are limited and mostly based on case studies. The objective of this study was to assess the impact of long-term submersion, aquatic environment, bone type and DNA extraction method on DNA quality and quantity. Bone samples (scapulae and ribs), collected every ~1000 ADD from a freshwater lake and river, underwent DNA extraction via ChargeSwitch^® gDNA Plant Kit and organic phenol-chloroform methods, and DNA quantitation using both TaqMan and SYBR Green-based quantitative PCR (qPCR) methods. Results suggest that in both bone types, quality of recovered DNA (i.e., degradation index) declined significantly with increase in submersion time. Among two bone types, quality of recovered DNA from scapulae declined faster than rib samples. There was no significant difference in recovered DNA quantity between bone types, DNA extraction methods, or locations but various interactions between these variables showed significant difference. Overall, it can be concluded that DNA can be extracted from waterlogged bone in sufficient quantity to generate an STR profile up to 4000 ADD.

A first for forensic genetics in Africa: successful identification of skeletal remains from the marine environment using massively parallel sequencing

In unrelated circumstances, two young adult males allegedly went missing off the coast of Cape Town, South Africa, within two months of each other. Weeks after the second disappearance, a decomposed human lower limb was recovered from a beach in Cape Town, followed by a washed-up decomposed hand three days later. An item of female clothing was found with the remains, and preliminary analysis of the skeleton indicated a female, leading to confusion regarding the possible identity of the decedent. Consequently, DNA analyses were requested to determine the biological sex of the remains, and whether the two sets of remains originated from the same individual. Various samples were collected, including bone, nails and swabs of soft tissue. DNA quantity and quality varied between sample types, with better results obtained from metacarpal bone and swab lysates. DNA profiling revealed a male sex, which suggests cognitive bias may have played a role in initial sex estimations. In addition, massively parallel sequencing confidently matched the two sets of remains (random match probability: 1 in 2.70 x 10³¹). These results were a first for Africa where massively parallel sequencing was successfully used and assisted in the identification of human remains, thus, affording closure to the next-of-kin. Moreover, this constitutes the first global report where soft tissue lysates from a marine decomposition case yielded full DNA profiles with a massively parallel sequencing approach.

The fate of human remains in a maritime context and feasibility for forensic humanitarian action to assist in their recovery and identification

The number of annual maritime fatalities reported in the Mediterranean has more than doubled in the last two years, a phenomenon closely linked to the increase of migrants attempting to reach Europe via the Mediterranean. The majority of victims reportedly never gets recovered, which in part relates to the fact that the mechanisms and interaction of factors affecting marine taphonomy are still largely not understood. These factors include intrinsic factors such as whether the individual was alive or dead at the time of submergence, the individual's stature and clothing, as well as extrinsic factors such including ambient temperature, currents, water depth, salinity and oxygen levels. This paper provides a compilation of the current literature on factors influencing marine taphonomy, recovery and identification procedures for submerged remains, and discusses the implications for the retrieval and identification of maritime mass fatalities as part of the humanitarian response, specifically humanitarian forensic action, to the consequences of the current migration phenomenon.