by Sue Black
A relatively new field of research has been reported in the last year or so concerning the necrobiome – the colonies of bacteria that flourish on the dead. Researchers sampling the bacteria from the ears and nasal openings of cadavers have found that, using next-generation metagenomic DNA sequencing, they may be able to predict TDI very accurately, perhaps to within a couple of hours, even where death has occurred days or weeks before. If this research withstands scrutiny, and the methodology isn’t too expensive to run, this new kid on the block may eventually displace the brothers Pallor, Algor, Rigor and Livor.
If a body remains undiscovered through these four phases it will begin to smell pretty bad. In the fifth or putrefactive stage, the cells start to lose their structural integrity and their membranes begin to break down due to the slight acidity of the body fluids. This is called autolysis (literally, ‘self-destruction’) and provides the perfect conditions for anaerobic bacteria to multiply and start to consume the cells and tissues. This process releases a variety of chemicals, including propionic acid, lactic acid, methane and ammonia, whose presence can be used to detect where a decomposing body has been hidden or buried. We’re all familiar with how cadaver dogs are used to search for bodies. Their noses are said to be 1,000 times more sensitive than those of humans and they can sniff out minute quantities of putrefactive scents. Dogs are not the only species with a highly developed sense of smell: rats have also been trained to respond to the odours of decomposition as, incredibly, have wasps.
With the increase in gas production, the corpse will start to bloat and – as some of the odiferous substances, such as cadaverine, skatole and putrescine, grow more concentrated – become irresistible to insect life. Blowflies, in particular, will have detected the putrefaction products within minutes of death, and begun searching for areas in which to lay their eggs, or oviposit, usually around orifices such as the eyes, nose and ears. The unmistakable stench of putrefaction is all-pervasive and insects identify it as a food source for both themselves and their future offspring. The continued build-up of pressure from within the putrefying tissues will lead to purging of liquid at the orifices and can occur to such an extent that the skin splits, allowing even greater access to insects and scavengers. The skin starts to change colour, turning a deep purple, black or an unpleasant green reminiscent of very heavy bruising, due to the decomposition of the by-products of haemoglobin degeneration.
Active and advanced decay, the sixth stage of decomposition, will be set in motion when the larvae hatch and maggot masses take full hold. They will begin in earnest to break down the tissues that have become their food source. Through phases of advanced decay and successive waves of insect, animal and plant activity, all the soft tissue will eventually be consumed. This stage sees the greatest mass tissue loss as a result of feeding and liquefaction into the surrounding environment. The process generates a huge amount of heat: a maggot mass of around 2,500 can raise temperatures to some 14°C above the ambient temperature. Beyond 50°C the larvae will not survive, so when the core of the maggot mass approaches this critical temperature, they will separate and break into smaller and smaller clumps to try to cool down. It is this constant movement away from the central core and the frenzy of insect activity that gives rise to the apt phrase ‘a boiling mass of maggots’.
The seventh and final stage is skeletonisation, where all the soft tissues of the body are lost, leaving only the bones, and possibly some hair and nails, which are made of inert keratin. Depending upon the environmental conditions, and with the passage of enough time, even the bones may be destroyed. We all, then, return to the elements from which we were formed at the start of our life. The planet has finite mineral resources and each of us is made up of recycled parts that we, in turn, give back to the chemical pool.
So how long does this after-death disintegration process take to complete? There is no simple answer. In parts of Africa, where insect activity is voracious and temperatures high, a human body can be rendered from corpse to skeleton within seven days. However, in the cold wilds of Scotland it might take five years or more. As the rate of corporeal decomposition will be influenced by climate, availability of oxygen, cause of death, burial environment, insect infestation, destruction by scavengers, rainfall and clothing, among many other factors, it is not surprising that determining the TDI can rarely be definitive.
The fact that decomposition may be significantly delayed, or indeed halted, either by accident or intent, can also affect the reliability of assessing TDI. Freezing can stop decomposition almost completely and as long as the body doesn’t thaw out too many times, recognisable features may remain for centuries. At the other extreme, dry heat, which dehydrates the tissues, can also preserve a corpse. These conditions account for the longevity of, for example, the mummies of Xinjiang and those found in the Spirit Cave in Fallon, Nevada. Chemicals are largely responsible for the prolonged preservation of the famous mummies of Egypt such as Rameses and Tutankhamun. Here, removal of the internal organs and the packing of the body cavities with herbs, spices, oils, resins and natural salts, such as natron, were highly skilled procedures.
Submersion in water, as in the case of bodies found preserved in peat bogs, can halt aerobic activity. The body becomes sterile, and in time the acidic nature of the peat dissolves away the skeleton, leaving behind the tanned leather skin, which may remain almost visually recognisable, even after centuries have passed. In the right conditions – temperature, water pH and oxygen levels – the fat in the body can, instead of putrifying, saponify and turn into adipocere, also known colloquially as grave wax, forming a permanent cast of fatty tissues. ‘Brienzi’, a headless male body fully encased in adipocere, was found floating in a bay of the Brienzer See in Switzerland in 1996. Analysis finally determined that he had drowned in the lake in the 1700s and his body had become covered in sediment. Two weak earthquakes in the area might have been sufficient to eventually dislodge him from his incarceration, allowing him to rise to the surface.
Some researchers have called for the building of additional human taphonomic facilities – more colloquially, and more repulsively, known as ‘body farms’ – where remains are left out in the open air and studied with the aim of providing researchers with a better understanding of the decomposition process. The US has six such facilities and there is one in Australia now, too, but I am not a supporter of the idea of a UK body farm. The arguments put forward to justify them do not sit comfortably with me. There is little evidence that the current method of using animal proxies, generally dead pigs, is inaccurate in establishing a TDI, or that the research from these human-based facilities has significantly improved our ability to predict it with any greater reliability. I would want proof of both to reconsider my position. I find the concept both gruesome and grim, and my unease is heightened when I am invited to take a tour of one of these places as if it were a tourist attraction. I am often asked why we don’t have a ‘body farm’ in the UK. I think the more relevant question is why would we need, or want, one?
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Whatever remains of our presence on earth, in death, our identity may be as important as it is in life. Our name – the very core of what we consider to be ‘me’ – can survive long after even our bones are gone, commemorated perhaps at our final resting place on a headstone, plaque or in a book of remembrance. It may be one of the least permanent constituents of our identity, yet it can outlive our mortal remains by centuries, and in some cases remain sufficiently powerful to inspire fear, loathing, love and loyalty in future generations.
A nameless body is one of the biggest problems for any police investigation into a death, and there is always an imperative to resolve it, regardless of how much time has elapsed between the death and the discovery of the body. Forensic scientists will attempt to link the physical remains with a name so that documentary evidence can be accessed, relatives or friends found to confirm the identification and the circumstances surrounding the death explored. Until this connection is
made, there can be no questioning of a person’s family, social circle or colleagues, no tracing of mobile phone activity, no examination of CCTV footage, no reconstruction of final journeys. Given the number of people who are reported missing every year – approximately 150,000 in the UK alone – it is no easy task. At its most basic level, our mission is to try to reunite a body with the name it was given at birth.
Generally, we will all have a name – if only our family name – before we are born. If not, we will be given one very soon thereafter. We do not choose it, nor has it been acquired by accident, and we are highly unlikely to be its first or sole owner. This marker, selected by someone else as a gift, or perhaps a curse, for us to carry for the rest of our lives, becomes a significant component of who we believe ourselves to be.
We respond to our names automatically and without hesitation, even at a subconscious level. In a noisy room, we might have difficulty following conversations but when our name is uttered, we hear it loud and clear. Very swiftly, it becomes an embedded aspect of the history of the ‘self’ we lay down as our life progresses and we may devote some effort, and occasionally significant sums of money, to protecting it from being misused or misappropriated by others.
And yet, despite the importance of our names to our identity, we routinely change them for all sorts of reasons – when we form new partnerships or families, or to separate a personal life from a professional one, or simply because we don’t like our birth name. Some people keep one name all their lives; others use two concurrently for different roles or go by a variety of them. Normally, when people choose to formally change their name, the transition is mapped out in traceable official documents; even so, it creates an additional layer of inquiry for forensic investigators.
When you factor in nicknames and abbreviations, one person can be known by a staggering array of labels. My own case is not untypical. I was born Susan Margaret Gunn. As a child I was Susan – or Susan Margaret, the full Sunday name, when I was in trouble, which was quite often. As I grew up my friends called me Sue. I married and became Sue MacLaughlin (Mrs, later Dr); then, on my remarriage, Sue Black (Professor, later Dame) – and for a very short time, to maintain publication continuity for my career, I was Sue MacLaughlin-Black (talk about an identity crisis).
Had my mother had her way, I would have been Penelope, for no other reason than that she liked the name Penny. Not only did I dodge the bullet of becoming known as Penny Gunn, I am grateful that this future forensic scientist did not have to live with the name Iona, lovely though it is when appended to the right surname. Happily, Susan Gunn seemed innocuous enough, although my family name was always going to be a target for exploitation when my initials came into play. Inevitably, perhaps, S.M. Gunn spawned the nickname Sub-Machine Gunn.
Since unique names are rare, most of us will share our most personal label with many others. Of over 700,000 Smiths in the UK, some 4,500 of them are called John. My own maiden name is not particularly common: last time I checked, there were only 16,446 fellow Gunns registered in the UK, most of them, not surprisingly, in the very north-east of Scotland around Wick and Thurso. Only about forty were called Susan.
Encountering a namesake can be amusing but obviously it can cause confusion. For actors, trying to pick a name nobody else is using to secure their Equity card must be a nightmare. When I acquired the name Black another Sue Black emerged on my horizon – a computer scientist who was instrumental in rescuing Bletchley Park from decline. Dr Sue Black OBE is a lovely lady of around my vintage. Although we have never met we have communicated by email, as on occasion I will get queries about Bletchley Park or invitations to give a lecture on codebreaking during the Second World War, and have to inform my very disappointed correspondents that they have ‘the wrong Sue Black’ and that, unless they want a talk on the dead, they might be best advised to speak to the real one.
Our fascination with identity is reflected the world over in folklore and literary tradition, where stories featuring disguise, assumed identity, mistaken identity or identity theft abound, not to mention foundlings adopted or exchanged at birth. Such themes are a feature of most of Shakespeare’s comedies; indeed, much of his work deals with the concept of identity in one way or another. They provide endless plot devices for exploring the nature of society, conflict and how human beings relate to each other.
These stories would have resonated more plausibly in the simpler societies of the past, where creating a new identity, or assuming one belonging to someone else, could be achieved with far less risk of exposure than would be the case today. The infamous sixteenth-century imposter who stole the identity of Martin Guerre, and who has inspired various books, films and musicals, could not have got away with it for so long in the modern era, where forensic science can confirm an identity almost to the exclusion of all others.
Yet there are still plenty of instances where a proverbial skeleton has rattled its way out of a family closet. To find out after many years that you are not who you thought you were can come as a tremendous shock and precipitate a genuine crisis of identity. Was my mother actually my sister? Was my father not my father? Was my father my grandfather? Was I adopted? Since our identity is built throughout our lives on the foundations laid down by those around us – those we trust to tell us the truth – our name and our heritage become the bedrock of our sense of self and our security. It can prove to be a house of cards. When a lie is exposed, everything we believe about ourselves and our place in the world can tumble down around our ears. Such discoveries are often triggered by a death, as relatives search through documents or investigators dig deep into a life to put a name to a body, or to try to understand the circumstances or motivations involved in how it ended.
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So when forensic anthropologists are faced with an unidentified body, how do we go about reuniting the deceased with their name? First we need to establish a biological profile: was this person male or female? How old were they when they died? What is their ancestral origin? How tall were they? The answers to these questions allow us to place an individual into a specific pigeonhole. Once we know that we are looking at a woman who was in her mid-twenties, black and around 5ft 6ins tall, we can search databases of missing people to see who might fit those broad criteria. There will be many candidates. One search performed for a white male, aged twenty to thirty and between 5ft 6ins and 5ft 8ins in height, returned 1,500 potential names in the UK alone.
There are three features recognised by the International Criminal Police Organisation (INTERPOL) as primary indicators of identity: DNA, fingerprints and dentition. While fingerprints and forensic dentistry have been used in forensic science for over a hundred years, DNA analysis, the new kid on the block, has been in our forensic toolbox only since the 1980s. We owe its practical application and its revolutionary impact on identification in police investigations, paternity disputes and immigration issues to the pioneering work of the British geneticist Sir Alec Jeffreys from the University of Leicester.
DNA, or deoxyribonucleic acid, is the genetic building block housed within most cells of the body. As half of our DNA is passed to us from our mother and the other half from our father, it has direct familial traceability. There is a common misconception that the recovery of DNA from a body will in itself always lead to a positive identification. But of course a comparison must be made, either with a source sample of the DNA of the person the deceased is suspected to be, if there is one on record, or with samples provided by direct family members (parents, siblings or offspring). The genetic link with a parent’s DNA would be equally as strong in, say, an estranged brother of the deceased, so if a family source is to be used it must be supported by other features of biological evidence specific to the missing person, such as their dental records.
When testing parents, we prefer if possible to use a mother’s DNA, as obviously there can be some doubt as to whether Dad is the natural father. Families come in all shapes and sizes and biological relationships are not a
matter for secrecy in many households, but as there are those where such a revelation could cause great upset, caution and discretion are always at the forefront of such investigations. As my worldly-wise granny used to say, ‘You always know who your mother is, but you only have her word for who your father might have been.’ That perhaps says quite a lot about my family. Whatever the circumstances, nobody needs the additional burden of unwelcome revelations when trying to come to terms with a bereavement.
A recent mass fatality, in which over fifty people lost their lives, provided a textbook example of how death and DNA analysis can expose family secrets. Two sisters were convinced that their brother had been caught up in the disaster, even though all hospitals had been checked and he was not registered as a patient at any of the accident and emergency facilities. They had not heard from him, and nor had any of his colleagues or friends; he was not responding to his mobile phone and neither were any calls being made from it. Over a week later, there had been no withdrawal from his bank account or use of any of his credit cards.
There was one unidentified, badly fragmented body in the mortuary that fitted this man’s general physical description, but the DNA did not match that of his sisters. Investigation would later reveal that the body was indeed their missing brother. Unbeknown to them, and perhaps to him, he had been adopted as a baby – a secret that was eventually confirmed by an elderly aunt. The sisters now had to deal with a double blow: the loss of their brother and the discovery that he was not their biological sibling. For them this raised disquiet about the identity of their sibling, their relationship to him and the honesty of their parents.