Estimation of the Time since Death

Current Research and Future Trends

Jarvis Hayman, Marc Oxenham

• Publisher: Academic Press
• Year: 2020
• Print ISBN: 9780128157312
• eBook ISBN: 9780128163689
• Topic: Law
• Subtopic: Forensic Science
• Index: Law

Estimation of the Time Since Death is a current comprehensive work on the methods and research advances into the time since death and human decomposition. This work provides practitioners a starting point for research and practice to assist with the identification and analysis of human remains. It contains a collection of the latest scientific research, various estimation methods, and includes case studies, to highlight methodological application to real cases.This reference first provides an introduction, including the early postmortem period, biochemical methods, and the value of entomology in estimating the time since death, along with other factors affecting the decomposition process. Further coverage explores importance of microbial communities in estimating time since death. Separate chapters on aquatic environments, carbon 14 dating and amino acid racemization, and total body scoring will round out the reference. The final chapter ties together the various themes in the context of the longest running human decomposition facility in the world and outlines future research directions.- Provides the first comprehensive reference to bring together all aspects of knowledge relating to the estimation of the post-mortem interval in decomposed human bodies- Contains real case studies that underscore key estimation concepts- Demonstrates the changing role of technology and advances in the estimation of time since death

Chapter 1

Approaches to time since death estimation

Jarvis Hayman, and Marc Oxenham School of Archaeology and Anthropology, Australian National University, Canberra, ACT, Australia

How to develop a more accurate estimation of the time since death in human bodies found decomposed or decomposing has exercised the minds of criminal investigators and others interested in advancing scientific knowledge since the first forensic cases described by Sung Tz'u in 13th century China [1]. When more intense interest in the subject developed in the 19th century, research first focussed on the recognition that the fall in the temperature of a corpse could be of use in determining the time since death in the early stages of decomposition [2–4], but it was French Army Surgeon and entomologist Jean Pierre Mégnin who recognised that different groups and species of insects were attracted to a decomposing body during the various stages of decomposition [5]. Of necessity, this led him to describe the different stages of decomposition in order to match them with the various species of insects appearing on a corpse at varying stages during its decomposition. Unfortunately, this led to his descriptions being used to convict people, often wrongly, of unlawful killing. In 1897 Murray Galt Motter, after a study of 150 disinterred human bodies in and around the Washington DC area in the USA, commented, in relation to using insect succession to estimate the time since death, that it was not possible to make any universally applicable generalisations and indeed it was not safe to draw any conclusion at all [6]. Although the study of entomology and its value in estimating the time since death in bodies found decomposed has advanced greatly since that time, especially in the last 30 years, there is still an error rate that invites caution when it is employed in criminal cases.

Since the 1950s when researchers increased their efforts to match temperature with the time since death and especially after the studies of Thomas Marshall and F. E. Hoare in the 1960s in their attempts to determine a mathematical model, there has been increased interest and research into all aspects of human decomposition. As new technological innovations have been introduced into scientific research, they have been employed in attempting to more accurately estimate the time since death [7–10]. These have included attempts to find a linear relationship between changes in biochemical substances with the decomposition of the corpse not only in the early stages but also in the advanced stages of decomposition; the use of microscopy and physicochemical methods of dating skeletal material such as chemiluminescence, the citrate content of bone and in the last decade, the use of body scoring methods to quantify the stages of decomposition.

The research published by Mary Megyesi and others in 2005 on a method of quantifying the stages of body decomposition with a Total Body Score gave a significant boost to attempts to more precisely determine the time since death in human bodies found decomposed [11]. Many studies since then have attempted to refine quantifiable scoring of the decomposed remains and to produce models incorporating the many variable factors which affect the rate of decomposition but to date the number of these factors such as temperature, moisture, context, scavenging etc. as well as the subjectivity of body scoring methods have defied efforts to produce a more statistically precise model. Attempts have also been made to define a “universal model” applicable to all situations in which a decomposed body is found but so far this has not been proved to be possible because the contextual and climatic situations in which a corpse may be discovered are so numerous and so varied that it may never be possible with present technology although the hope is that it may become feasible in the future with the development of quantum computing [12,13].

The following section provides an overview of the chapters presented in this volume. As will be seen, some focus on very specific postmortem stages with the initial chapters following a progressively longer timeline after death. Subsequent chapters discuss a range of both new or developing approaches and techniques to estimating TSD, some of which will be quite novel to some readers. We have attempted to be as thorough in our coverage as possible, with some techniques, or versions thereof, being commonly employed in forensic case work, while others are much more experimental and largely untested in the courts.

Roger Byard, in Chapter 2, begins the substantive part of this volume by reviewing research on estimating TSD in the early postmortem period (or 24–48 h), although some of the techniques reviewed can be utilised within the first 24 h (e.g. algor mortis, or the more or less predictable decline in body temperature in the early postmortem period). Indeed, the Hensgge nomogram remains the preferred method. Livor mortis, generally used to identify body position after death, and rigor mortis changes over time are also discussed, both approaches to TSD estimation being dependent on a wealth of variables most of which will be difficult to control for. The process of autolysis and putrefaction are briefly described, with a detailed description of how ‘stages’ in this process can be utilised for TSD estimation dealt with in Chapters 5 and 10. Roger also notes the limited value of using gastric emptying (evaluation of stomach contents) in determining the time since a last meal. Also mentioned is the lesser known, in the West at least, use of mechanical and electrical muscle excitation techniques for TSD estimation, approaches that perhaps require more replicative research. Overall, Roger provides a wealth of techniques of varying levels of accuracy and precision in the estimation of TSD within the first two days postmortem.

In Chapter 3 Lena Dubois and Katelynn Perrault explore the value of biomarkers in estimating TSD, the core premise being that measurable biomarkers change (increase or decrease) in a predictable and relatively standardised manner during the postmortem interval. Perhaps one of the most well know of such approaches is analysis of the concentration of potassium in the vitreous humor of the eye, which is arguably useful up to 72 h postmortem. A wealth of other biomarkers have been analysed, both sourced from within the body itself (e.g. ammonia and nitrogen concentrations) and others from decomposition products that have seeped into the immediate environment (e.g. phosphorous and sodium) with varying degrees of value in TSD estimation. In terms of preservational durability, and thus the ability to be sampled, adipose tissue lipids and by-products have received considerable attention in recent years. Again, such biomarkers can be sampled from the body directly or from the surrounding burial matrix (generally soil). Proteins, including enzymes and protein metabolism by-products also appear to be of value in examining the postmortem interval (PMI). Some of this protein-focused research has revisited work on the vitreous humor with promising outcomes. The premise that DNA and RNA degrade in a regular and measurable manner postmortem has also received attention in recent years. It would seem that the rate of decay is dependent on various factors, including tissue type and temperature and despite a wealth of recent research, the approaches are still experimental rather than of practical use in case work. Decomposition odour (volatile organic compounds, VOC) is an important variable in insect colonisation succession patterns and it is not surprising that research into the measurement of VOCs released by the decomposing corpse has shown some promise in the estimation of the TSD. Practical approaches include recent work on trimethylamine concentrations in postmortem tissues. Lena and Katelynn finish their chapter with a consideration of the practical value of biomarker research to date, in as much as proposed methods can pass evidentiary standards. Their conclusions are sobering, because only a very few of the hundreds of biomarkers assessed to date consistently provide useful TSD estimates.

James Wallman and Melanie Archer review the role of insects in estimating TSD, an approach that can extend the assessable postmortem window substantively beyond the first 48 h. The underlying premise in forensic entomology is that particular species will colonise and utilise a corpse for a finite period of time and that the subsequent changes to the decomposition fluids and tissues will provide a more suitable ecosystem for subsequent colonisation by different species (whether insect or other factor-moderated): a process termed succession. James and Melanie begin by introducing the key insect players, those that have evolved to a point where they rely on locating and colonising decomposing animals in order to reproduce: for the most part certain fly and beetle species. It is important to note that it is a minimum PMI that is being estimated as it is often difficult or impossible to determine the lag period between death and subsequent initial insect colonisation. Apart from insect succession, James and Melanie discuss the role of specific species maturation (e.g. stage and size) in developing an estimate of the minPMI. A range of confounding factors are also discussed, including the issue of insect species identification which can have significant flow on effects in calculating the minPMI. Other issues include seasonality and weather, including retrospectively generated temperature estimates with temperature being a significant variable in insect activity and reproduction rates. A significant portion of James and Melanie's chapter is given to procedures, and associated issues, with insect collection methods and processes. This is particularly pertinent in cases where sampling is not being carried out by the forensic entomologist. The Chapter concludes with a series of forensic case studies that illustrate the role and value of forensic entomology.

In Chapter 5, Eline Schotsman, Wim Van de Voorde and Shari Forbes tackle the complex issue of estimating TSD when a body has reached an advanced state of decomposition. In noting the difficulties inherent in estimating TSD with advanced decomposition they stress the importance of context, not least of which is the effect of temperature (and humidity) in either accelerating (higher temperatures) or slowing (cooler temperatures) decomposition. The environmental context (e.g. soil) has a major influence on decomposition rates, and thus estimation of TSD, particularly in terms of its ability (or inability) to facilitate microbial action, gas exchange and moisture movement. Apart from faunal interference (e.g. vertebrate scavenging), human body disposal behaviours (e.g. by embalming or being confined in a coffin) will affect the rate and nature of decomposition. Moreover, individual characteristics such as sex, age, and body size will influence decomposition rates to varying degrees in different burial environments. Eline and colleagues also discuss the effects and predisposing conditions for preservation (e.g. mummification, freezing, saponification) of soft tissues and how such issues can be dealt with. The intriguing case of bog bodies, the context of which is generally well known among northern European archaeologists, is also mentioned. They discuss the important issue of differential decomposition (and preservation), which should be taken into consideration when assessing total body scores (TBS usually assumes uniform rates of decomposition throughout the entire body, including the external appearance) for the decomposition of the entire corpse. A significant portion of the chapter reviews and critiques current methods for estimating TSD using either formulae and/or a TBS with a substantive comparative test of such approaches using a complex case study. They conclude by suggesting more regional models of decomposition are better suited to TSD estimates and that specialists need as broad a knowledge base as possible to deal with this vexing problem.

David Carter's chapter departs from a focus on techniques with a particular or specific value at various periods postmortem when he examines the role and value of microorganisms in estimating TSD. David begins by looking at microorganisms and microbial communities and one way in which that can be of value in estimating TSD: microbial community succession (a concept of particular importance in forensic entomology). Unlike the case with insects, a body will harbour an antemortem microbial community that will change at death, clearly requiring an understanding of such communities prior to death. Microbes not only contribute to the processes of decomposition, but microbial succession tracks important stages in this process, one key event being the major microbial succession event following rupture of the body tissues caused by the production of putrefactive gas. Importantly, microbial action can continue significantly beyond the early postmortem period, well beyond the timeframe of traditional forensic entomological approaches. Indeed, microbial communities play a role in bone degradation with some promise of extending the window of TSD estimation significantly. An advantage of using microbes is that sampling can take place by way of standard swabs and species identification can be carried out using DNA identification techniques. The use of microbes in TSD estimation is perhaps one of the most exciting and promising areas of research at present in this discipline.

In Chapter 7 Alyce Cameron and Marc Oxenham explore the value and range of approaches to estimating TSD using skeletonised remains. In general, approaches focus on methods that seek to identify levels of organic remains preserved in skeletal material and those that examine the physical breakdown of the non-organic components of bone. For instance, UV fluorescence seeks to identify proteins that may still be preserved in bone, although the value of the approach lies more in being able to differentiate between recent and much older (>100 years) remains. Other tests, such as chemiluminescence which can identify iron in haemoglobin, has had varying success and clearly requires much more research as does work on citrate content of bone and rates of DNA degradation in bone. Other techniques, such as Infra-red and Raman spectroscopy, which can identify the molecular structure of bone, while having a significant role in other areas of medical and forensic science have yet to make a significant impact on the estimation of the TSD, although they certainly seem to be a promising area of further research. When considering the decomposition of bone structures, Alyce and Marc note that histological techniques exploring surface bone changes show some promise, particularly with respect to changes in surface pores over time. They note that weathering has received a considerable amount of attention, but a wealth of variables (not least climate and general environmental factors) may play a significant role in the development of a general model of weathering and TSD estimation. Clearly, estimating TSD in skeletonised remains is fraught with difficulty, but current research appears promising.

The next chapter, by Felicity Gilbert and Marc Oxenham, explores current research into estimating TSD in aquatic environments. The fir...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• About the editors
• Chapter 1. Approaches to time since death estimation
• Chapter 2. Estimation of the time since death in the early postmortem period (24–48 hours)
• Chapter 3. Biochemical methods of estimating time since death
• Chapter 4. The application of insects to the estimation of the time since death
• Chapter 5. TSD estimation in the advanced stages of decomposition
• Chapter 6. The importance of microbial communities in the estimation of the time since death
• Chapter 7. The postmortem interval and skeletal remains
• Chapter 8. Estimation of the TSD in an aquatic environment
• Chapter 9. Radiocarbon and amino acid racemization (AAR) and the time since death
• Chapter 10. The development of grading systems to determine human decomposition: Total Body Scoring of decomposed human bodies in indoor settings
• Chapter 11. The future of taphonomic research
• Index