The most important thing I took away from the Murder, Mystery and Microscopes event at the Edinburgh Science Festival last week was: Don’t bother to commit a crime – you will get caught. The notes below are therefore not intended to aid you in any criminal activity but may be of interest if you read or write crime fiction.
Stuart MacBride read out three extracts from two of his books then invited forensic experts David Barclay and Lorna Dawson to “demonstrate whether there is any possible truth in the nonsense I put in my novels.” To his credit, MacBride’s descriptions were mostly accurate.
- Extract 1 (Cold Granite): A body is found at a rubbish dump. In the book a group of school children have the misfortune to stumble upon a dead body poking out of a bin bag at the dump. Barclay talked us through the correct procedure for locating a body in a rubbish heap, should no curious school children be available. First you would have to have some clue to suggest that the body had indeed ended up there; blood in a wheelie bin, for example. Every day truck loads of rubbish would have been added to the heap so that since the body was dumped, the front face of the heap would have crept forward by several meters. You would have to take core samples starting from the face of the heap and working backwards until you found newspapers from the date when the supposed victim went missing. You would then take core samples going across the heap until you found envelopes with a postcode on them corresponding to the address the bloody wheelie bin belonged to. This method relies on people throwing out old newspapers and envelopes with their household rubbish which lead Barclay to comment, “If recycling catches on it will be the worst thing ever for forensic scientists.”
- Extract 2 (Dying Light): A body is found in woodland. Lorna Dawson explained how you would pinpoint where a body had been hidden if you suspected it had been transported by car to somewhere remote and dumped. First you would take samples of soil from the tyres of the suspect’s car. Using information from the National Soil Database you could overlay maps of soil pH, mineral content and vegetation to identify areas where the soil could have come from. “Generally criminals are lazy and don’t want to carry the body far so it is usually found no more than 100m from where the car was parked.” A body dumped in woodland could be scavenged by animals. In this case you would call in experts on foxes or badgers to help track down the missing body parts.
- Extract 3 (Dying Light): Arson attack. Barclay told us that MacBride was spot on when he described the perpetrator masturbating in the bushes after throwing a petrol bomb into a house. “It’s surprisingly often that we find semen on leaves of bushes near crime scenes.” MacBride was also right to have the perpetrator breaking the window of the house with a brick before throwing the petrol bomb in since “they normally bounce off windows.” However, petrol bombs are not the neatest way to commit arson. Where would the arsonist get the petrol? Barclay pointed out that garages are covered by CCTV so there would be evidence to show him or her buying it. Petrol is messy. It would splash onto the arsonist’s clothes and police may find his or her footprints in the petrol residue at the crime scene. Petrol is extremely explosive when it vaporises so the aronist would have to act quickly if they didn’t want to blow themself up. Finally, when petrol burns it goes up and away from clothing and bodies leaving evidence behind for the police to find.