Case reviewBodies in sequestered and non-sequestered aquatic environments: A comparative taphonomic study using decompositional scoring system
Introduction
A primary task of any death investigation is the reliable estimation of the post-mortem interval (PMI) which is the time elapsed between death and the recovery of the body also known as time since death [1]. For bodies in aquatic environment the PMI is also called post-mortem submersion interval (PMSI). In this regard, it is widely accepted that terrestrial decomposition differs from aquatic decomposition [2]. In fact, sea water usually slows up putrefaction [3], mainly because of the cooler aquatic temperatures compared with terrestrial temperatures, the salinity or salt concentration reducing the bacterial action, and the protection from insect and small mammal predators [4], [5]. However, aquatic environments can deeply affect the rate of post-mortem decay as well as the preservation/dispersal of bodies submerged commonly exposed to different changing conditions like currents, marine animal activity and, water temperatures which can be considered relatively constant depending mainly on depth of submersion [6], [7]. Unfortunately, in the forensic context there are only few studies dealing with marine taphonomy and the fate of human remains in aquatic environment [8], [9], [10], [11], [12].
In 1972, Payne & King [13] first focused on the soft tissue disappearance and loss of body parts using fetal pigs carcasses submerged. Later, Haglund [8] reported the general pattern of soft tissue disappearance and disarticulation of eleven human remains found submerged in salt water and fresh water, by using a skeletonization scoring system (SSS). The SSS was adopted looking for the regional presence of soft tissue, exposure of bone, and disarticulation at the head, neck, hands, forearms, upper arms, feet, legs, pelvic girdle, and trunk. Using pig models in the marine context, Canadian authors [14], [15], [16] observed that most invertebrate faunas are opportunistic scavengers and fed on the remains at all time so that no classic succession of invertebrate species can be determined in contrast with insect colonization in terrestrial environments. In deeper experiments, pig carcasses were skeletonized in less than a month due to animal activity whereas for shallow carcasses the remains were not skeletonized for many weeks [16].
It has been noted [1] that most of the scientific papers dealing with PMI as well as PMSI estimation as case studies on human remains or animal models “have never gained any practical relevance since they do not meet the demands in practice (being precise, reliable and giving an immediate result)”. Therefore, a need for validation studies of PMSI estimates based on human decomposition in water environments has also been raised [17], [18]. A more quantitative approach and the inclusion of statistics in a science that is primarily descriptive have been proposed [19], [20] in order to avoid the common scientific controversy in estimating the PMI and PMSI in forensic practice and/or in courtroom proceedings. In this regard it has been demonstrated that decomposition stages and PMI can be predicted with accuracy from temperature records and that a reliable degree-day index can be developed [20]. In fact, not only in terrestrial decay but also for bodies submerged, the study of decomposition by using accumulated degree days (ADDs) can be useful to estimate the PMSI [18], [19], and regression equations have also been calculated. ADDs are a summation of temperatures over time (days) or better the accumulation of thermal energy needed for the chemical and biological reactions of decomposition to take place [21]. Since 1967 a strong correlation between time of immersion, water temperature and signs of decomposition has been demonstrated by Reh [22] as recently reported [23]. ADD can be easily derived from a total aquatic decomposition score (TADS) according to descriptive decompositional scoring system (DSS) provided by Heaton et al. [18] based on forensic cases of human bodies recovered from the U.K. waterways. Although these authors [18] already warned about the effect of adipocere on the accuracy of their model because of delaying the appearance of later decompositional characteristics, the purpose of this comparative taphonomic study is to verify how useful can be the TADS for ADD prediction in two series of bodies submerged in sequestered and non-sequestered aquatic environments. In this regard, several forensic taphonomy researchers [18], [19], [20], [21], [24], [25], [26], [27] have used this method recently with great optimism to account for the variability in the level of decomposition in humans, but none of these researchers have achieved the same levels of correlation and accuracy.
Section snippets
Materials and methods
A total of 68 human remains cases have been selected based on their marine site of recovery: 16 bodies of the first series were found mostly floating or submerged in shallower sea waters, 52 bodies belonging to the second series were all victims of a single shipwreck, all found in sequestered environments of the relict in deep cold water.
Results and discussion
The final scores assigned to the study group, according with DSS, are illustrated in Table 3 for sequestered and non-sequestered series of bodies. In both series of bodies, inter-examiner variability was no longer than one score for most of the anatomical regions. Only for a few of assessments not in agreement (a couple of scores for the first series and 6 cases for the sequestered bodies), a re-evaluation was then performed until final correspondence.
Most of the 68 victims were in relatively
Conclusion
Usually forensic pathologists and investigators try to evaluate the state of decay in a body to provide an approximate time estimate in order to limit the potential list of missing persons. However, the general pattern of decay observed in water-related deaths is the effect of several circumstances dealing with the body (age, size and clothing) but mainly with environmental factors among which cold temperatures, depths, currents, ecosystems and, aquatic animal activity [4], [8]. For example,
Acknowledgments
The authors gratefully acknowledge all the forensic pathologists, anthropologists and autopsy technicians who worked on bodies at the Section of Legal Medicine, University of Bari. The authors also thank the anonymous reviewers for their relevant and precious comments.
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These authors have contributed equally to this paper.