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CSI: Geophysics

If you came across someone burying dead bodies in a field, you’d be right to call the police. Unless the grave digger in question was a forensic geophysics researcher.

Forensic geophysicists help the police hunt for objects hidden underground or underwater: anything from crime weapons to murder victims. For researcher Dr Jamie Pringle of Keele University, this means burying cadavers in order to test different methods of detection.

Thankfully, we’re not talking about human bodies here but pigs. These farmyard animals have a lot more in common with us than you’d think, making them perfect study subjects. ‘They’re good analogies for us: they have a similar body size, organ size, fat to muscle tissue ratio and skin type,’ explains Pringle.

So how do you go about finding a dead body? Crime statistics show that the majority of murder victims are hidden inside buildings (in walls or under floors), about a quarter are dumped in water, and only 10 to 15% are buried.

If a burial is suspected, the police employ sniffer dogs and metal detectors to scope out the area. In some cases, this is all that’s needed to find the body.

‘A lot of clandestine burials are done in a panic and those are easy to find,’ says Pringle. When dealing with more well thought out murders, it can be much more difficult, and this is where geophysics can come to the rescue.

With police investigations time is always of the essence, so the key is evaluating the conditions and working out which method is most likely to work. This is what Pringle’s work with pigs focuses on.

Seeing underground

The most widespread forensic geophysics technique is Ground Penetrating Radar, or GPR. Initially developed to detect landmines, it got its first big break in 1994, when it was used to locate the victims of serial killers Fred and Rose West.

GPR works by sending electromagnetic waves into the ground and timing how long they take to bounce back. The waves are reflected if they hit an object, so geophysicists can tell whether there is anything unusual in the soil, and if so, how deep it is.

Although GPR can be highly effective in building up an image of what lies under investigators’ feet, it’s not suitable for all situations.

Firstly, to clearly distinguish something buried underground there needs to be enough contrast between the object you are looking for and the soil around it. ‘If you’re looking for a gun in a metal scrap yard, you’re not going to find it,’ comments Pringle.

GPR’s success rate also depends on variables such as soil type, how long the body has been buried, and whether it is naked or clothed. Pringle’s study found for instance that a pig wrapped in tarpaulin was easier to find than a naked one.

Despite a few high profile successes, the use of GPR by the police remains relatively uncommon. ‘I think the technique’s fairly well known, it’s just that it’s sometimes incorrectly applied,’ says Pringle. In consequence GPR often gets dismissed because it fails to live up to expectations in difficult conditions.

Luckily, forensic geophysicists have more than one trick up their sleeves. Alternatives to GPR include measuring electrical resistivity: the soil’s ability to resist an electrical current.

‘As you decompose, your tissue and blood will mix with the soil water and give a very conductive leachate,’ explains Pringle. As a result, an electric current will flow more easily through a patch of ground where a body is buried, allowing geophysicists to spot potential graves.

Identifying which method to use when is a key aim of Pringle’s studies on pigs. It’s certainly not a job for the squeamish, but as far as forensics research goes, it could be much worse. In the US, where regulations over the use of human tissue are less strict, over 120 people per year reportedly donate their bodies to the country’s largest ‘body farm’ for studies into the gruesome field of human decomposition. Any volunteers?


Find out more about Jamie Pringle's research at Keele here.

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