Every Contact Leaves A Trace… (picture courtesy of Hertfordshire Constabulary)

The Anatomy Of Crime

13th March 2015

Every contact leaves a trace… Kathy Walton spends a day in forensics.

“Sometimes it takes just one killer piece of evidence to solve the case; sometimes it’s like building up a jigsaw with dozens of little pieces…” Karen Georgiou, 44, head of Scientific Services (and thus responsible for a team dealing with forensic examination, recovery and analysis) for Hertfordshire, Bedfordshire and Cambridgeshire Police, is introducing me to a fascinating – and sometimes frustrating – world of crime detection.

Her colleagues at Hertfordshire Police HQ in Welwyn are gathering evidence following a robbery in Watford. “It was a highly organised high-value robbery at night,” she explains. “We retrieved a lot of forensic information [from the scene]: fingerprints, hair and spittle and ran these profiles against our DNA database.”

However, unlike television detective programmes, where they always seem to get a ‘hit’ straight away, the regional database initially failed to come up with a match, so the information must now be fed into the national database.

I’ve jumped at the opportunity to meet Karen and her team because I’ve been fascinated by forensics ever since I spent a day in a lab at the HQ of the Royal Canadian Mounted Police with a forensic scientist cousin, nearly thirty years ago. In fact, so impressed was I by my visit, I resolved never to embark on a life of crime, mainly for fear of being found out.

I remember being shown how an analysis of just one hair or drop of blood could link me to (or eliminate me from) a crime scene, and even picking up a few tips on how to spot a marked playing-card or loaded dice. Since we were in the wheat belt of Canada, I was also shown how microscopic markings on a single grain of wheat could help prove that a truck load of the stuff was stolen from a particular grain store.

Clever stuff, forensic science. So amazingly clever that I wondered then, and still do, why they don’t teach it in schools as a crime prevention measure – think of how many potential young criminals it might help to keep on the straight and narrow.

As well as being clever, forensics is also ‘good stuff’, according to Val McDermid, whose recent non-fiction book Forensics: The Anatomy of Crime is every bit as compelling as her detective novels.

If you have ever wondered where McDermid finds the ideas for her plots, she gives us a clue in the preface to Forensics, where she acknowledges her debt to forensic science, which, over the past 200 years, has helped uncover the facts behind seemingly unsolvable cases. ‘The application of science to the solving of crime is the reason I am gainfully employed,” she says, “…because their work has transformed what happens in courtrooms all around the world.”

One of the earliest forensic cases cited by McDermid occurred in 1794 in Lancaster, when a surgeon examining the victim of a fatal shooting proved that a wad of paper, used to secure the powder in the gun and later found in the wound itself, matched a torn sheet of paper in the suspect’s pocket – and the culprit was nailed.

In the mid 1800s, British chemist James Marsh devised the first reliable test for arsenic, which sent many a Victorian poisoner to the gallows. His method was effective enough to detect even the tiniest trace, and it’s still in use today.

One to fall foul of it was Durham miner’s daughter Mary Ann Cotton, who was eventually hanged in 1873, having killed at least 21 people – husbands, lovers, her own mother, children and stepchildren – usually in order to cash in their life insurance policy. (Significantly, the French dubbed arsenic ‘poudre de succession’ – inheritance powder). Cotton was this country’s most prolific killer for over a hundred years… until surpassed by the notorious Harold Shipman, the Manchester GP found guilty in the year 2000 of murdering at least 210 of his patients. Forensics played its part here, too. Only when the daughter of one victim became suspicious about the unexpected nature of her mother’s will was the body exhumed and found by forensic scientists to contain a fatal dose of diamorphine, a powerful painkiller.

Shipman had also incriminated himself by leaving his fingerprints on the forged will, typed on his own machine, unwittingly substantiating what forensic science seeks to prove, namely that ‘every contact leaves a trace.’ The words are often attributed to pioneering French forensic scientist Edmond Locard (1877-1966), and although he didn’t phrase it precisely like that, his philosophy and practice were such that the idea is now known as Locard’s Exchange Principle. ‘It is impossible for a criminal to act,’ he wrote, ‘especially considering the intensity of a crime, without leaving traces of this presence.’

The traces that he and his admirer, American forensic scientist Paul L Kirk (1902-1970), describe are ‘silent witnesses’ to robberies, rapes, road accidents, murders and acts of arson or terrorism. When crime scene investigators arrive at the scene in their paper suits, gloves and protective masks, it is their job to search for – and collect for later analysis – traces of sweat, semen, fibres of clothing, splinters of glass, fragments of paper, shoe and finger prints, hair and blood splatters, anything that will help them work out what happened.

With this in mind, I am shown into the fingerprint bureau at Welwyn HQ, which employs no fewer than 24 people whose job it is to get a ‘lift’: a print ‘lifted’ from a crime scene. Each print is enhanced with powders, fluorescent dye or even superglue (a technique devised by a police forensic scientist in Bedford in the 1980s) and then lifted by adhesive film, before being either manually compared to finger prints from a known suspect, or scanned and encoded by computer. The print’s individual characteristics are then matched against the regional or national database.

While I was there, a fingerprint expert initially found 15 possible matches for a print, before further verification singled out the ‘one’ – a process which can take 60 minutes, far longer than the cop shows on TV would have us believe. Amazingly, I learn, forensic sciences has become so sophisticated that powders can now identify thieves’ finger prints on the feathers of protected birds.

The scientists I spoke to joked that their working lives would be so much easier if real life forensic work were as straightforward as it looks on the screen – no delays, no complications – but as Val McDermid points out in her book, watching crime programmes does have its uses. She gives the example of a rape victim from Wiltshire who, in 2011, deliberately left crime scene evidence that helped convict her attacker. After raping her, the man made her clean herself up with towels, but by cleverly copying a trick she’d seen on the American series CSI, the victim deliberately left strands of hair and spittle on the car seat.

The perpetrator was subsequently found guilty, both of this rape and of five previous sexual assaults, thanks to the astonishing presence of mind of the victim and to the expertise of forensic scientists, who recognised ‘a killer piece of evidence’ when they saw it.

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