Forensics

by Val McDermid

  If the oldest maggots can’t be found, because they are already flies, then the entomologist can draw on Jean Paul Megnin’s nineteenth-century insights about the predictable waves of insect colonisation. As a corpse begins to dry, different fly families, such as cheese flies, flesh flies and coffin flies, make it their home. When a corpse becomes too dry for a maggot’s mouth hooks to rake, beetles arrive armed with chewing mouth parts. They eat the dry flesh, skin and ligaments. Finally, moth larvae and mites go to work on the hair, leaving only a skeleton to signify the life that once was. All of these species work to their own timetables, which the entomologist can harness to help estimate the length of time since death.

  In 1850 a plasterer discovered a mummified child behind a mantelpiece in Paris. The young couple living there were initially suspected of murder but, when Dr Bergeret d’Arbois looked at the insect evidence, he contended that the body had been ‘exploited’ by flesh flies (which differ from most other flies in that they are ovoviviparous – that is, they deposit hatched maggots, rather than eggs, into decaying matter or open wounds) in 1848, and mites had laid eggs on the dried corpse in 1849. Suspicion then fell on the former occupants of the house, who were arrested and subsequently convicted.

  In some cases, the puzzle faced by the investigators is nothing to do with the time of death. In a recent case in Merseyside, police were searching a suspect’s house when they came across a large collection of empty pupal cases. They speculated that these could have been the result of a dead pigeon in the loft, but it seemed odd that there were the remains of so many pupae. But there was no way of interrogating the dark brown cases to discover when they had cracked open to free the newborn flies. Then someone had the bright idea of sending the cases off for a toxicology examination. The results were startling. The cases contained traces of heroin metabolites. There’s no history of pigeons ingesting heroin, so further tests were ordered. Martin explains: ‘Maggots feed in a soup of DNA, and they have spines on their bodies which tissue gets lodged in. The pupal case is the old skin of the maggot and may still have human tissues on it.’ When the pupal cases were examined further they revealed traces of human DNA which matched that of a known drug user who had been reported missing. On the basis of this and other evidence, the owner of the house was convicted of murder and jailed for life. He had disposed of his victim, but could not silence the insect witnesses.

  More conventionally in forensic entomology, the time of death can sometimes play a decisive role in a court case. One day in the park, a 10-year-old British girl, Samantha, met a man of about thirty. He gave her sweets and befriended her. When she got home Samantha told her mother what had happened. Her mother didn’t seem too concerned about her daughter’s new acquaintance. A while later the girl met the man again and this time he invited her back to his house. Nothing terrible happened. The pair met like this regularly. They would go for walks, or watch TV, sometimes with a few of the man’s male and female friends there, too. Eventually the girl invited the man back to her mother’s house. Before long, the mother and the man began having a relationship. The man spent some weeks with the mother, before beginning to abuse Samantha sexually. The household filled with bitter resentment. Vicious rows flared up between the three of them. And then Samantha went missing.

  The police conducted a search and finally uncovered the girl’s body in a mound of rubble and broken bricks in the grounds of a hospital. A ferocious blow from a heavy blunt object had caved in the left side of her skull. The distinguished forensic entomologist Zakaria Erzinçlioğlu was summoned to the scene to examine the body. He discovered some freshly laid eggs and minuscule blowfly maggots. These offered evidence that the girl had died very soon after she was last seen with the man. In court the man pleaded not guilty. But halfway through the proceedings, as the maggot evidence was being presented, the man broke down and confessed. He had silenced the girl in the middle of an argument, after she had threatened to tell her mother about what he was doing to her.

  Zak Erzinçlioğlu has helped to solve 200 homicides in his 30-year forensic career, and has written about many more, but his quirky memoirs, Maggots, Murder and Men (2000), cover much more ground than the title suggests. For example, he records a peculiar incident in Finland. One morning, a government official walked into his office to find some large maggots underneath the edge of the carpet. He summoned his cleaning lady and asked her when she had last cleaned his office. When she said ‘last night’, he fumed at her and accused her of lying. He simply couldn’t believe that such big ‘bugs’ could have appeared overnight. He fired her on the spot.

  But the official, a typical bureaucrat, preserved some of the maggots and eventually took the opportunity to show them to a professor at Helsinki University. He identified them as blowfly maggots in the wandering stage. They had finished feeding, probably on a rat elsewhere in the building, and wriggled off to find somewhere to pupate. They could indeed have arrived in the office overnight. The mortified official contacted his old employee in a state of remorse, offering to restore her to her former job.

  In the end, it all comes down to placing science at the service of justice. It’s about taking facts which have been hard won in the abstract world of the laboratory and using them in the uncompromisingly real world of the crime scene. ‘In an academic environment you don’t encounter these sort of things,’ explains Martin. ‘But there is a great satisfaction to be got from applying my knowledge of insects to help in a fairly short timespan. Many scientists, not just entomologists, beaver away for years and years and years and don’t necessarily see an outcome from what they do; whereas I can generally see within a few months that something I’ve done has actually been of help.’

  Martin also recalls one case in Yorkshire, in which an elderly man had sold all his fine antique furniture for next to nothing to a stranger who had talked his way into his house. The confidence trickster told the old man that the furniture was infested with woodworm, showed him maggots on the floor to prove it, and left with his booty. Distraught, the old man called on his neighbour, who spotted some of the maggots still on the floor. He bottled them up and gave them to the police, who in turn passed them on to Martin. The maggots were promptly identified as crane fly larvae – better known as Daddy Longlegs – which like to feed on grass roots and are completely uninterested in wood.

  Martin said, ‘Fortunately, the guy who stole the furniture was found and it was returned to the old man. Even this brusque Yorkshire policeman was quite emotional when he was telling me how excited the old guy was when he got his stuff back. Again it was just through knowledge of insects.’ So happy endings rooted in knowledge are out there; but entomological evidence can be a slippery thing, especially in the adversarial world of the courtroom.

  On Friday, 1 February 2002, Brenda Van Dam went to a bar with two friends in San Diego, California, leaving her husband to babysit their three children. Brenda arrived back home at 2 a.m. She only noticed that her 7-year-old daughter, Danielle, was missing from her bedroom when she went to wake her up the next morning. Panic seized her. The last time she had seen Danielle was the previous evening, when the little girl had been writing her diary, while her father and brothers played video games.

  The police interviewed neighbours and discovered that David Westerfield, an engineer who lived two doors down from the Van Dams, had driven his motorhome away for the weekend. Everybody else in the neighbourhood had been at home. It emerged that Danielle and her mother had knocked on Westerfield’s door a few days earlier, selling Girl Scout cookies. He was placed under 24-hour police surveillance on 4 February. Police investigated his motorhome and found child pornography, some of Danielle’s hair, fingerprints and a smudge of her blood. After a search involving hundreds of volunteers, Danielle’s naked body was found on 27 February in a dry, brushy area by the side of a road. Her shrivelled, leathery skin had almost entirely mummified.

  David Westerfield stands during a plea hearing in a San Diego Superior Courtroom
in February, 2002. He pled not guilty to a charge of murdering Danielle van Dam, his seven-year-old neighbour

  Insect evidence became a key focus of the trial. An unprecedented four entomologists were called to testify. Very few maggots had been found inside Danielle’s body. The entomologists called by the defence said that flies must have laid their eggs in mid-February. The defence lawyer argued that, as this was a week after Westerfield had been placed under police surveillance, he couldn’t have dumped her body at the roadside. The prosecution lawyer accused the defence entomologist of using incorrect weather data. He sneeringly asked him how much he was being paid, implying that he was a ‘hired gun’, which led to such a blazing row that the session had to be adjourned early.

  Entomologists called by the prosecution dated the blowfly infestation to 9–14 February, still some days after Westerfield was put under surveillance on 4 February. But, they argued, other factors might explain the late arrival and small number of insects found on the corpse. The extremely dry weather – the driest in more than a century – had sucked the moisture out of Danielle’s body, making it less attractive to maggots. A blanket may have been covering the body which could then have been carried away by dogs. Perhaps ants had taken away the eggs and maggots that had arrived earliest to the corpse. These ideas were refuted by an entomologist for the defence.

  David Westerfield was found guilty of kidnapping and murder. And put on Death Row. The average wait between sentencing and execution is sixteen years in California. He protests his innocence to this day. In 2013, he made an official appeal for a new trial, which has yet to be heard by the Supreme Court.

  The conflicting conclusions of the four experts involved in the Westerfield case did damage to the reputation of forensic entomology. There is no evidence that any of them were ‘hired guns’. Rather, they had a particularly difficult set of circumstances and variables to deal with: a small number of maggot specimens; conflicting reports about the extreme weather; intense media scrutiny. Only one of the entomologists was actually given the chance to examine the body in situ. Science usually works best when it is approached collaboratively. If those scientists could have compared their findings in an unpressured environment – as often happens now in the UK system – the range of their estimations would likely have been reduced.

  Since the Buck Ruxton ‘Jigsaw Murders’ in 1935, the UK public’s appreciation of forensic entomology has grown steadily. And now, thanks in part to the international success of crime television shows such as CSI, whose main character, Gil Grissom, frequently uses insects to solve crimes, forensic entomology is more widely recognised than ever. Real life entomologists continue to dream up astonishing ways of using their science to extract forensic evidence. In a recent case in the US, the movements of a suspect were identified by the insects splattered on the wind-screen of his vehicle.

  But such breakthrough techniques are not the norm. Most of the forensic entomologists’ work is based on a detailed assimilation of a huge volume of information and the ability to differentiate between insects that most of us would dismiss as identical. Entomologists turning to forensics enter an emotionally and intellectually complicated place. Their knowledge and methods are stretched to the limit as they try to read minute biological clocks under their microscopes. Getting informants to hand over their secrets is a tricky business, no matter what their species.

  FOUR

  PATHOLOGY

  ‘To begin depriving death of its greatest advantage over us, let us adopt a way clean contrary to that common one; let us deprive death of its strangeness; let us frequent it, let us get used to it; let us have nothing more often in mind than death.’

  Michel de Montaigne, Essais (1580)

  The poet John Donne reminds us that ‘Any man’s death diminishes me, because I am involved in mankind’. It’s a line that carries moral weight but, in spite of that, it is undeniable that we are more affected by sudden violent death when it has some connection to our own lives, however tangential. So it is for me with the case of Rachel McLean, who was an undergraduate at the same small Oxford women’s college that I attended. Although I never knew her, I can’t escape a sense of distant kinship with her and her fate.

  Rachel McLean was an undergraduate at St Hilda’s College when she became John Tanner’s girlfriend at the age of nineteen. Tanner proposed to her on 13 April 1991, ten months into their relationship. A momentous occasion like that would surely be something any girl would be eager to talk about with everyone who is close to her. But over the next few days none of her friends at St Hilda’s or in the wider university saw Rachel. She was both a studious and a friendly, open person; nobody could quite believe she’d have gone off somewhere without telling anyone. Tanner phoned the house where she lived, saying he wanted to speak to her but her housemate said she didn’t know where Rachel was.

  After five days of growing concern, the college authorities reported Rachel missing to the police. When they contacted Tanner in Nottingham, where he was studying at the university, he explained that he’d last seen her on the evening of 14 April 1991, when she had waved goodbye to him from the platform at Oxford station as his train left for Nottingham. A long-haired young man they’d met in the station buffet had offered her a lift back to her digs in Argyle Street.

  Tanner co-operated with the police, helped in the searches and took part in a television reconstruction of his departure from Oxford station to try and jog the memory of anybody who might have seen Rachel. He’s believed to be the first murderer ever to take part in such a televised reconstruction. In an emotional press conference he told friends and reporters that he and Rachel were in love, and planning to get married.

  But the police suspected that Tanner was hiding something, so they had briefed reporters to ask him key questions, such as ‘Did you kill Rachel?’ The way he answered, smirking and with a lack of emotion, made the police feel sure he knew more about her disappearance than he was willing to admit.

  They searched the house in Argyle Street that Rachel shared with friends. Everything appeared to be in order; the floorboards hadn’t been tampered with and nothing else looked suspicious. The detectives were desperate to find evidence that they could use to arrest Tanner, or at least to put pressure on him. Frogmen searched the River Cherwell and other officers scoured nearby scrubland.

  They contacted the local council to check whether the house on Argyle Street had ever had a cellar. The answer came back that, although there was no basement, some of the houses on the street had been underpinned, which meant that there were spaces underneath the floors.

  Armed with this information, the police searched the house again on 2 May. This time they found Rachel’s partially mummified body under the stairs. Tanner had squeezed her through a 20 cm gap at the bottom of the stair cupboard, and pushed her underneath the floorboards. Although it had been eighteen days since her death, she had barely decomposed; warm, dry air coming through the airbricks had dried her skin.

  Finding the body is the end of the first phase of a murder inquiry. But it’s only the beginning of the forensic pathologist’s crucial contribution to the building of a case against the defendant. In the Rachel McLean case, that task fell to Iain West, head of the Department of Forensic Medicine at Guy’s Hospital. During the autopsy, he found a 1 cm bruise to the left of Rachel’s larynx and four 1 cm bruises to the right. He took photographs of these, and of petechiae – tiny haemorrhages in her face and eyes. His internal examination revealed fractures of the laryngeal cartilages in the throat. All of these traumas were indicators of death by strangulation. There was also a tuft of hair missing from her scalp, which West believed Rachel had torn off in a desperate attempt to relieve the pressure on her throat.

  When the police confronted John Tanner with the damning evidence from Iain West, he broke down and confessed to killing Rachel. At his trial he said, ‘I flew at her in a rage and proceeded to put my hands around her neck. I think I must have lost control, because I have onl
y a vague recollection of the time that elapsed afterwards.’ He claimed he had killed Rachel after she had admitted to being unfaithful. Then he spent the night lying next to her lifeless body. In the morning he searched for a suitable place to hide her, dragged her through the gap in the cupboard, and caught a train back to Nottingham. Tanner was given a life sentence. He returned to his native New Zealand upon his release in 2003.

  Forensic pathology resembles a jigsaw puzzle. The pathologist has to catalogue any unusual elements found on or inside a corpse and, from those fragments of information, try to reconstruct the past. Throughout human history, people have wanted to understand why those they care about have died. The very word ‘autopsy’ derives from the Ancient Greek for ‘seeing for oneself’. An autopsy is a medical attempt to satisfy that profound curiosity.

  The first known forensic autopsy took place in 44 BC, when Julius Caesar’s doctor reported that, of the emperor’s twenty-three stab wounds, only the one between his first and second ribs was fatal. A couple of centuries later, the Greek physician Galen produced hugely influential reports based mainly on dissecting monkeys and pigs. Despite his raw material, his theories on human anatomy remained uncontested until Andreas Vesalius started comparing normal and abnormal anatomy in the sixteenth century, paving the way for modern pathology, the science of disease.

  When Vesalius published his landmark book on anatomy, De Humani Corporis Fabrica (On the Fabric of the Human Body), in 1543 he dedicated it to the Holy Roman Emperor, Charles V, whose reign also saw another landmark in forensic medicine. For the first time in the history of the Holy Roman Empire, rules of criminal procedure were enacted. They regulated which crimes should be regarded as serious, allowed for the burning of witches and, for the first time, gave the courts the power to order investigations and inquisitions into serious crime. Known collectively as the Carolina Code, crucially for forensic medicine, they required judges to consult surgeons in cases of suspected murder.