FORENSIC science鈥檚 spell in the limelight has given it huge kudos. Glitzy TV shows like CSI: Crime Scene Investigation have sent students flocking to forensics courses. But while this interest is sexing up the image of scientists, is it also stopping police catching criminals and securing convictions?
鈥淛urors who watch CSI believe that those scenarios, where forensic scientists are always right, are what really happens,鈥� says Peter Bull, a forensic sedimentologist at the University of Oxford. It means that in court, juries are not impressed with evidence presented in cautious scientific terms.
Detective sergeant Paul Dostie, of Mammoth Lakes Police Department, California, found the same thing when he conducted a straw poll of forensic investigators and prosecutors. 鈥淭hey all agree that jurors expect more because of CSI shows,鈥� he says. And the 鈥�CSI effect鈥� goes beyond juries, says Jim Fraser, director of the Centre for Forensic Science at the University of Strathclyde, UK. 鈥淥versimplification of interpretations on CSI has led to false expectations, especially about the speed of delivery of forensic evidence,鈥� he says.
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Another problem caused by media coverage of forensic science is that it informs criminals of the techniques the police employ to catch them. 鈥淧eople are forensically aware,鈥� says Guy Rutty, of the Forensic Pathology Unit at the University of Leicester, UK. For this reason, some forensics experts are reluctant to cooperate with the media.
There is an increasing trend for criminals to use plastic gloves during break-ins and condoms during rapes to avoid leaving their DNA at the scene. Dostie describes a murder case in which the assailant tried to wash away his DNA using shampoo. Police in Manchester in the UK say that car thieves there have started to dump cigarette butts from bins in stolen cars before they abandon them. 鈥淪uddenly the police have 20 potential people in the car,鈥� says Rutty.
None of this makes the forensic scientist鈥檚 job any easier, but it probably won鈥檛 prevent them fingering a suspect, says Carlton Jones, a business manager at the UK鈥檚 Forensic Science Service. 鈥淔orensically aware criminals are not something we have to really worry about.鈥�
For one thing, it is extremely difficult not to contaminate a crime scene, even by wearing protective clothing. Police officers鈥� DNA is automatically excluded from the inquiry to avoid the problem of falsely accusing them of a crime. Rutty tested just how easy contamination is by asking a volunteer to walk around a sterile room and repeat a phrase.
鈥淧olice say car thieves have taken to dumping cigarette butts from bins in stolen cars before abandoning them鈥�
Rutty was able to retrieve the subject鈥檚 DNA even though the man had been in the room for only a few seconds. Contamination occurred even if the subject was wearing a face mask of the kind used by crime scene investigators.
Trying to outwit forensic science is scarcely new. In 1988, the world鈥檚 first case involving DNA almost failed because the murderer persuaded a friend to submit a sample on his behalf. Only when the stand-in bragged about the cover-up was a DNA match made.
Bull for one doubts that even a forensic scientist could get away with murder, such is the variety and sensitivity of the techniques available to investigators. A forensically savvy criminal might set them on a false trail initially, but that鈥檚 the best he can hope for, he says. 鈥淚f you want to commit the perfect murder there鈥檚 one thing I鈥檒l ask you,鈥� he says. 鈥淒o you feel lucky, punk?鈥�
