Forensic investigations: Can a fly solve a murder case?

By Ken Eastwood 3 August 2009
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Forget the glamour of prime-time television. Forensic investigation is a precise science based on careful – and sometimes malodorous – research.

GET BLIND DRUNK IN the tropics and even the maggots will tell stories about you. If you fall down comatose during the day you’ll lie very, very still – much more so than when sleeping. Within two hours, flies will realise you’re not moving, and deposit live larvae in your ears, nostrils or under your armpits. You’ll wake with a nasty itch, and the size and age of the maggots will spell out, almost exactly, how long you’ve been lying there drunk.

Using maggots and other insect informants to help solve a crime is called forensic entomology, a small but increasingly respected brand of science. In Australia, there are only two places to study it at the postgraduate level: Griffith University in Queensland and the Centre for Forensic Science at The University of Western Australia (UWA), Perth.

The latter institution sits on a quiet hill above the rest of the UWA campus. In the coffee room, P.D. James and Patricia Cornwell crime novels sit alongside theses on blood spatter and books on criminal law. A human figure is outlined on the floor in the foyer, as in a crime scene.
“He was one of the builders – that’s what happens if you don’t do a good job around here,” says director of the centre Professor Ian Dadour, deadpan.

Ian is one of 30 forensic entomologists in the world who give evidence in court. He teaches the FBI about the recovery of human remains, and lectures at conferences worldwide.

Western golden-haired blowfly (Photo: Jiri Lochman)

Western golden-haired blowfly (Photo: Jiri Lochman)

“My expertise is in restricted-access areas such as cars and wheelie bins – bodies in wheelie bins,” he says. His laptop has a number of macabre photos to prove it.

Possibly as a reaction to investigating and probing things that make even the toughest coppers squeamish, Ian is an over-the-top character, full of life and with conversation constantly punctuated with swearing, bawdy remarks and black humour. He gives his lectures titles such as “Have you ever dated a dead person?” and “101 uses for a maggot”, and wanders back and forth like a caged bear, brandishing his pointer like a weapon when delivering them. He has personally given forensic evidence in every Australian State and Territory except Victoria and South Australia.

“What I do is measure things,” Ian says. “Against all the other techniques, forensic entomology is the gold standard. I’d like to think it’s more accurate than most.”

With intimate knowledge of the approximately 75 insect species that visit decomposing corpses in Australia – their life cycles, the order in which they arrive, and how temperature affects their development – Ian reckons he can pinpoint time of death to within 6–8 hours, even up to a month after the event. He contrasts the work of pathologists – medical doctors who give estimates of time of death based on their experience – with his work measuring maggot size, pulling fly eggs out of putrefying matter, and identifying all the species of insect crawling on, under and in the corpse.

“By the time you explain what you do and give your results, the jury is looking at you like you’re one sick bastard,” he says. “The Australian public tends to believe medicos, rather than evidence from scientists who measure maggots.”

But in some cases guilty parties have expressed surprise that he pinpointed the timing so precisely. “I rarely attend corpses in the mortuary [in Perth] but my services are utilised in many other States and countries. I just don’t think the tools we use are regarded that highly but times are changing.”

Ian describes a case in which a body was found in a house burnt down on a Saturday night. During his investigations on the Sunday morning, he found maggots on a bloody quilt in a bin. He proved the maggots were at least three days old, so calculated the blood was from the previous Wednesday. The police changed their investigation to focus on that day, and learned that the victim and his brother had had a violent argument in the house then. The brother was arrested, and confessed to killing the victim on the Wednesday. Once again, the maggots told the full story.

Fingerprints and fragments

There are at least 23 scientific disciplines in forensics, from psychological profiling to DNA analysis, being studied at UWA. Here, John Watling uses analytical chemistry to help solve crimes. By identifying trace elements in material – whether fragments of glass, clothing, explosives or the sticky tape found on a cocaine shipment – the bespectacled professor can trace its origin. “We’ve had a murder that was committed with a fence picket and rust fragments in the wound can be related back to a specific picket,” he says. “We are even able to distinguish between glass made on a production line an hour apart.”

In 1976, John developed “gold fingerprinting”, using a $500,000 piece of machinery called a mass spectrometer. This technique means that a suspicious gold ingot or piece of jewellery can be tested to determine its origin, even if it has been melted down and purified. Gold fingerprinting has been successfully tested in court several times in Australia, the UK, USA, New Zealand and Indonesia. A similar technique is used to solve cases of diamond theft and, increasingly, the forgery of high-end market collectibles such as Ming dynasty porcelain. “You know how you tell if it’s Ming?” John asks jokingly, holding up a beautiful hand-decorated bowl. “You hold it up like this and hit it with your finger and if it goes ‘mingggg’ then it’s authentic.”

Chemical fingerprinting involves taking a speck of the material and splitting it into its different atomic elements. The tiniest portions of unusual suites can reveal where something came from. One of the growing uses of this technique is in food forensics, where the integrity of regional brands is big business. French champagne producers have fought hard to keep the Champagne brand and don’t want inferior substitutes being sold as theirs. The Australian food export industry doesn’t want to be tarnished by material from elsewhere that is potentially contaminated and falsely sold as Australian.

“We’ve had cases where Australian milk was being sold in South America, and some of that milk wasn’t Australian,” John says. The science is now becoming so precise that John and his team can determine not just what country or region wine came from, but in what vineyard the grapes were grown. “In the past 10–15 years we’ve increased our analytical sensitivity by a thousand times and the next generation will go better than that.”

DNA techniques are also changing, through an understanding that an entire DNA molecule isn’t needed to make a conclusive match. As 99.9 per cent of our 3 billion base pairs of DNA are the same, a forensic DNA specialist such as the UWA’s Silvana Gaudieri can focus on small sections that do vary. By matching 9–15 sections, reliability of DNA matches can be expressed in the terms of “one in a billion or one in a trillion”.

“All you need to get DNA is cells,” Silvana says, picking up her phone. “My holding this mobile phone – we shed cells and leave cells – that can be enough. Someone else could leave cells on the outside of a cigarette.”

In perhaps the most contemporary application of forensic DNA techniques, Silvana is researching ways to trace the transmission of viruses such as HIV. Virus DNA mutates quickly, so someone infected with HIV six months ago will have quite different HIV DNA to the person who passed on the infection. “Viruses mutate about one million times faster than we do,” she says. “It’s hard to say how long it would take till that relationship [between transmitter and infected] is unrecognisable.”

In another laboratory at UWA, physical anthropologist Daniel Franklin (pictured above) is surrounded by skeletons and skulls. He can pick up any one bone and tell you the story of its original owner – this one suffered a gunshot wound to the head, this one had a fatal car crash, this one was an old person who had a hard life. By studying particular bones he can formulate a biological profile, which involves determining the sex, approximate age, stature and possibly the ethnicity of the person. He can also provide some insight into the life history of a person up to their demise, including old injuries, diseases and degenerative changes such as osteoarthritis.

Daniel’s work has included identifying some of the 400-year-old skeletons of people stranded after the 1629 wreck of Batavia on a reef in the Houtman Abrolhos, off the WA coast, but he’s also become involved in more contemporary cases to help determine the age of individuals from their bones. “At the end of the day you can never find out the entire truth. In a lot of forensic cases the only way you really know is when someone confesses,” Daniel says.

At the scene

On a stinking hot Sunday, 20 minutes drive south from Perth, a slight breeze carries the sick stench of death. A rotting corpse with police tape surrounding it lies in a sandy clearing among pigface, gums and paperbark in a nature reserve on the southern outskirts of the city. Ian Dadour badgers a group of mainly international forensic students as they tentatively capture maggots, flies and beetles from the body that’s been rotting out here for six days.

The corpse in this case is a 40 kg pig, one of nearly 450 that Ian has watched decompose in the reserve, determining how factors such as clothing, burial and temperature make a difference to the progression of insects and the rate of decomposition. In summer, a body in this temperate climate becomes a skeleton in about four weeks. In winter, it can take five months. In the tropics, just 15 days.

Ian correlates his research with work undertaken at the so-called Body Farm, The University of Tennessee Forensic Anthropological Research Facility, USA. Until recently, it was the only place in the world where forensic researchers could study how humans decompose. Rotting pigs are the closest match. “To my nose, humans smell a bit sweeter,” Ian says.

Evidence of Ian’s decomposition experiments is spread around the UWA reserve. There are cages where fresh-dead pigs were hung to replicate suicides, and skeletons that have been there so long there’s virtually nothing left but a scattering of bones and the elastic from a pair of shorts. “I think there’s been a serial killer – there are a whole lot of bodies out here,” jokes Dr David Cook, the forensic centre’s research officer.

In one experiment, some of the pigs were covered by vegetation, which led to a 24-hour delay in insect activity. Ian has also left dead pigs in cars, which led him to determine that in about 70 per cent of cases temperatures in cars are about 20°C higher than the ambient temperature outside. So although insects might take 20–60 hours longer to reach a body in a car, the rate of decomposition can be much faster after they’ve done so.

The research is proving that insects can tell much more than just time of death. Even a year or so after the flesh has gone from a skeleton, residue in fly-pupae casings can indicate whether the corpse had high drug levels in its system, or higher than expected levels of lead, barium or antimony, which would indicate a death by shooting.

Forensic entomology, or “frenzied” entomology as some call it, is not just about dead bodies, either. About twice a month in summer Ian gets a call when someone finds a maggot in food they’ve bought. “I can tell you I wouldn’t eat at a lot of places around Perth – we’ve done most of them,” he says. In one big case, workers from a large mine went on strike because maggots were found in the sugar. But Ian studied the maggots and deduced, with a high probability, that they had been placed there by humans. “These were from a fly that lays live maggots; so why would it lay its maggots in sugar where they’re going to die?”

Away from the rotting pigs, in a laboratory that smells like bad parmesan cheese, David studies the life cycles at different temperatures of relevant fly species. “Out in the field they probably only live a couple of weeks, but here flies can live for up to three months,” he says. They need sugar and water to survive, but to start laying eggs they need two protein meals, which David supplies in the form of fresh, bloody livers. “The first time you give them liver, they use all of that to develop the eggs. We then leave them for a week, then give them more, and they lay.”

To investigate how quickly flies can strike, David left dead guinea pigs in the bush near Perth for periods of one hour, two hours and three hours, and then covered them up so no more insects could get in. Even some of the guinea pigs that were left for just one hour were soon crawling with maggots. “Within one hour, these flesh-flies and the blue-bodied blowfly are in the eyes, ears and anus – they’re right into it,” David says.

Researcher Sasha Voss is studying the wasps associated with corpses. She has discovered that in the Perth area, four wasps come in to parasitise the immature stages of flies, laying their eggs inside the pupae. “The flies are the first to arrive, but their development finishes after about four weeks. Because the wasps come in later it extends the time we can work with,” she says. “The use of wasps is very new – we have very little reference data. Until recently we didn’t even know what species were relevant to forensic cases.”

One puzzle she’s still hoping to solve lies in the cues that cause wasps to arrive at remains; somehow they know that not only is there a body, but that fly maggots are at or near the pupae stage. “It’s definitely odour based, some odour is released from the maggots feeding on the carcass – some by-product is released,” Sasha says.

Too close to home

Australia has about 360 homicides a year and about 20 per cent of the corpses are found with insect material on them. Even in most of these cases, a forensic entomologist such as Ian – who is not a member of a police force – is not called. Occasionally he’s sent photos and can help identify species and age of insects from these, but he says that’s far from ideal. Still, in the past decade he’s personally attended about 165 crime scenes and worked on at least 600 human cadavers.

“The only time I’ve been affected was a case with an 11-year-old boy, and my son was 11 at the time,” he says. “I had to pick maggots off the hand, and it was the same size as my boy’s hand. It was heart-rending. But you’ve got to put it behind you and do the job.”

Source: Australian Geographic Issue 95 (Jul – Sep 2009)