Estimating the time of death is notoriously challenging, and it is often essential to understanding the crime and securing a conviction. The provision of these estimates is often based upon the stages of decomposition as traditionally defined during the post-mortem. The people examining the remains will look for features such as body cooling, lividity, the presence of feeding insects such as blowflies and, in later stages, putrefaction. Increasingly, these observations are also being supported by the work of forensic entomologists like the team at the Natural History Museum, as well as other specialists.
For most of us decomposition is a horrible thought. It triggers alarm bells in our minds about the risk of infection and robustly reminds us of our mortality. Nearly every horror novel or film will have decomposition as a stock means of triggering fear. But decomposition is a complex and amazing biological process. As we decay, different communities of bacteria and other microbes compete for space and food. In ecology, this idea of transition is called ‘succession’. Succession can be seen everywhere in the natural world. For those of you who are gardeners, colonisation of your freshly dug flower beds is an early successional stage. Leave things long enough and annual weeds will give way to perennial one, which in turn will largely be replaced by shrubs and then trees.
Decomposition is a very similar process to succession in the wider environment. Early successional stage microbes will compete for the most easily acquired food sources, the simple sugars and carbohydrates that pervade our bodies. As more and more of us is consumed, the microbes that are able to process complex compounds, such as the proteins in our ligaments and cartilage, will become ascendant. Those that consumed the simple sugars and carbohydrates will diminish and fade away and they too die. Finally, we are bones. Yet even these are home to organisms that have evolved to digest the tough composition of our skeleton. Bacteria and fungi are amazingly diverse and many of them are extremely specialised.
The complexity and diversity of the microbial world is increasingly being explored with the aim of furthering our understanding of the post-mortem interval. The increasing awareness that decomposition is successional and therefore chronological has opened up the world of the decay-causing organisms as a means of better estimating the post-mortem interval. Recent technological advances in sequencing DNA have made retrieving data practical and faster. Importantly, the advent of relatively cheap DNA sequencing has made it more affordable for scientists to explore these complex communities of organisms. Detailed study of the biology of decomposition is so recent − most of the work having been done since 2010 − that there are two alternative terms used to describe it. Both ‘Necrobiome’ and ‘thanatomicrobiome’ appeared in the scientific literature at roughly the same time, although the former appears to be the more widely used term. They both describe the communities of microbes found on and within us after our death. These microbes are an essential component of the decomposition process
The number of scientific publications in this area is still small but some conclusions are emerging. The primary external factor that significantly alters the rate of internal decomposition is temperature, although water and humidity may also have some impact. If we can establish the average temperatures of a wood where a body has been lying, potentially we have the means to estimate how long someone has been dead. Research using DNA sequence data has shown that the microbial community within the body changes significantly during decomposition. For example, the abundance of the members of the bacterial genus Clostridium increases as the body decays. This is also one of the reasons poorly stored meat is potentially dangerous: Clostridium bacteria produce several compounds that are highly toxic to humans. There is also a point where the rupturing of the body releases nutrients into the adjoining environment and increases the pH of that environment. We are probably a few years away from a ‘microbial clock’ being used as evidence in court, but I believe the approach will become standard before too long.
The microbial clock within our bodies is reflected in the responses of the living communities that surround us after death. I quite often hear people suggest that it is possible to detect a clandestine burial by the increased growth of the plants above or nearby. Unfortunately, reality is far more complex than that relatively simple proposition. Around the world, several scientific studies using experimental grave plots containing either pig carcasses or empty placebo graves have been done. In many instances of both cases, the plants respond to disturbance of the ground and grow more vigorously. The most likely cause for this is probably the release and mobilisation of soil nutrients caused by the act of digging a hole and disturbing the soil structure. This is comparable to the process of cultivation in gardening or agriculture.
If roots are unable to reach the body and the immediate area surrounding it, deeper burials are unlikely to affect the growth of the plants. Plants gain nutrients in a very different way to animals. Simply put, plants take sunlight energy, carbon dioxide and water and build carbohydrates such as sugars. They gain energy, via sunlight, by building simple molecules into more complex ones. Animals survive by doing the opposite, we take complex organic compounds and break them down into simpler compounds. The early stages of decomposition result in the production by bacteria of breakdown compounds, of which many are quite complex and probably toxic to plant growth. It is only during the latest stages of decomposition that the breakdown compounds become available for plants to metabolise. In most circumstances, it is probable that at first the presence of a dead body inhibits plants growth, but as time progresses, there may be an increase in growth. The complexity of this system is increased when we consider the potential impacts of soil type or other organisms such as fungi and invertebrates in the ecosystem. The whole topic is deeply fascinating and requires considerable research. Ideally, to do this there is a need for a body farm to be set up in this country so that the environmental and ecological interactions upon the dead can be properly studied here. Body farms are places where scientists can study the processes of decomposition upon the human body. People donate their own bodies with the aim of supporting important scientific research into what happens to us after death. The farms particularly aim to emulate murder or disaster scenarios. Probably the most famous body farm in the world is the one in Tennessee. There are now facilities in several locations across the USA, Australia and the Netherlands. Hopefully, we will establish one in the UK as well. Body farms are valuable for understanding how causes of death such as traumatic injury or drowning are affected by decay. They are also valuable for understanding how the necrobiome develops. While scientists can do experiments on donated human tissue in laboratories or on proxies such as pigs, they are a poor substitute. It is important to be able to work with the donated remains of people. Thankfully, a growing appreciation of the value of this work means that many people are willing to donate themselves after their demise. I have a feeling I may consider this. I have always fancied the idea of a sky burial, where our remains are placed in the open so that wild scavengers can feed upon us. In some parts of the world this role is performed by vultures. Sadly, in many regions, vultures are now critically endangered owing to diclofenac poisoning (diclofenac is used in veterinary practices as a painkiller); the vultures are killed by the diclofenac-impregnated carcasses of domestic animals. In some species, over 95 % of the vultures have been eradicated with serious environmental and human health consequences. Fewer vultures means that more carcasses are left for jackals, foxes and feral dogs to feed off; and because of the resultant increase in their populations there has been a rise in the number of rabies cases in some areas. Clearly, there are no vultures in southern England, but perhaps a nice farmer will lay me out so that I can feed the local red kite population. I’d like that.
The future of environmental forensics looks promising and exciting, but only if we can overcome the very significant public and research finance challenges that prevail. The recent advances in environmental DNA and ancient DNA technologies have the potential to revo
lutionise how crime scenes are managed. Exploring how the microbial community alters our remains after death through the gradually expanding international research community of body farms is very likely to help investigators improve their estimation of time of death. All these advances, when supported with robust and consistent exhibit collection and documentation, have the potential to place environmental forensics at the heart of thoroughly presented and verifiable evidence in court. These novel approaches must be developed alongside traditional skills based upon the ability to identify plants (and other organisms) in a crime scene and the understanding of how they may be evidentially relevant.
My time in the world of forensic botany continues to be unexpected and fascinating. Our planet is full of amazing life, and the plants we walk by nourish and enrich our lives. I’m very lucky that I can wander down the road, enjoying the diversity of plants around me, open the gate to my allotment and sit at ease in my greenhouse. Within my greenhouse, I can contemplate the latest batch of seed I have germinated. This year, I’m particularly chuffed with the five varieties of tomato I am growing, and in a week or so, I’ll be able to eat the first ones, fresh off the vine some forty-eight years after my father left the ones from the sewage plant on the kitchen table.
It is an honour to be able to use my knowledge to help seek justice for those whose lives are prematurely shortened because of the actions of others. My knowledge has evolved over decades watching and wondering, often with the love and support of family and friends. By the time I was twelve, my mother had become expert at the emergency stop while driving. Sat in the front passenger’s seat, gazing out of the window, I’d suddenly let out a shriek, calmly she’d say ‘where?’ and excitedly I’d say, ‘back twenty yards’. Mum would then reverse the required distance and I’d leap out and jump into the ditch. This was how I first saw meadow crane’s-bill (Geranium pratense), one of our most beautiful wild plants. Entering the world of forensic botany has reinvigorated and enriched my relationship with plants. Not only do I now spend a lot more time paying them intimate attention down a microscope, I also look at them differently. I’ll often find myself musing on the growth forms of plants, how the branches relate to one another, or how they might regrow after being damaged when people commit crimes. I am acknowledging that after well over forty-five years of gazing at plants, I still have a huge amount to learn.
Finally, I have the greatest admiration for those who work tirelessly, every day of the week, for many years at a time, trying to solve serious crimes and gain justice for the victims and their families and friends. They deserve our gratitude. But most of all, I will remember the dead. They have changed my life.
Acknowledgements
I wish to thank my forensic anthropologist colleague and friend ‘Sophie’, she has been incredibly important to me in guiding me along this bramble strewn, muddy dark path. The work that forensic specialists and police force staff do is immensely tough; anyone who can work on serious crime cases such as murder and remain composed deserves our respect and gratitude. Standing on freezing cold roadsides with detectives, PolSAs and CSMs, I’ve learned a lot, a very big thanks to all of them.
To my former editor Zena Alkayat I owe special gratitude, this book would not have come to be without her. Thanks also to Susannah Otter who took up the challenge of being my editor and to Steve Burdett who gave some editorial guidance. A huge thanks to my lovely agent Douglas Keane who was brave enough to withstand the occasional rant and listened to me waffle on over a glass or two of wine. To Edward my lovely partner, I’m deeply grateful for his love and patience and very constructive criticism of various drafts. Also, my brilliant bibliophile friend Debbie for telling me that an early version of this book was ‘not shit’ – from her that was an accolade which spurred me on! Also, lots of love to my mum and family who are mostly too squeamish to read this book. Thanks to my former colleagues and friends at the Natural History Museum, especially Julie Gray, Dave Williams, Martin Hall and Amoret Whitaker. Thanks also to Wenbo Chen for his translation.
This work is not an academic work, and early on, I decided to anonymise most people, both living and the dead. I made some exceptions to this rule when discussing well publicised cases that I had not participated in. Consequently, I have not mentioned many of the brilliant scientists whose work has contributed to the development of environmental forensics. In reparation for this omission. and as a means of allowing the more curious reader to learn more, I have provided a brief reading list.
Reading List
David O. Carter, Jeffery K. Tomberlin, M. Eric Benbow and Jessica L. Metcalf (eds.) (2017) Forensic Microbiology (Forensic Science in Focus)
David W. Hall and Jason Byrd (2012) Forensic Botany: A Practical Guide (Essential Forensic Science).
Stuart H. James, Jon J. Nordby and Suzanne Bell (2014) Forensic Science: An Introduction to Scientific and Investigative Techniques
Julie Roberts and Nicholas Márquez–Grant (2012) Forensic Ecology Handbook: From Crime Scene to Court (Developments in Forensic Science)
Patricia Wiltshire (2019) Traces: The memoir of a forensic scientist and criminal investigator
Publishing Director Sarah Lavelle
Editor Susannah Otter
Designer Nikki Ellis
Head of Production Stephen Lang
Production Controller Katie Jarvis
Published in 2019 by Quadrille, an imprint of Hardie Grant Publishing
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Cataloguing in Publication Data: a catalogue record for this book is available from the British Library.
text © Dr Mark Spencer 2019
cover photography © Kim Lightbody 2019
design © Quadrille 2019
eISBN 978-1787134010
Murder Most Florid Page 17
