Television shows scramble forensic evidence
連續劇的故事內容都是虛構的. 當人把內容當真, 後果有點不堪設想呢…… 監證連續劇播太多, 連疑犯都懂得去小心不讓警察找到抓人的證據啦~ 可惜, 故事裡面不一定是真的. 所以警察還是有其他辦法抓人的…..
(from New Scientist)
Television shows scramble forensic evidence
10 September 2005
Rowan Hooper
FORENSIC science’s 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?
“Jurors who watch CSI believe that those scenarios, where forensic scientists are always right, are what really happens,” 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. “They all agree that jurors expect more because of CSI shows,” he says. And the “CSI effect” goes beyond juries, says Jim Fraser, director of the Centre for Forensic Science at the University of Strathclyde, UK. “Oversimplification of interpretations on CSI has led to false expectations, especially about the speed of delivery of forensic evidence,” he says.
Another problem caused by media coverage of forensic science is that it informs criminals of the techniques the police employ to catch them. “People are forensically aware,” 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. “Suddenly the police have 20 potential people in the car,” says Rutty.
None of this makes the forensic scientist’s job any easier, but it probably won’t prevent them fingering a suspect, says Carlton Jones, a business manager at the UK’s Forensic Science Service. “Forensically aware criminals are not something we have to really worry about.”
For one thing, it is extremely difficult not to contaminate a crime scene, even by wearing protective clothing. Police officers’ 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.
Rutty was able to retrieve the subject’s 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’s 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’s the best he can hope for, he says. “If you want to commit the perfect murder there’s one thing I’ll ask you,” he says. “Do you feel lucky, punk?”
From issue 2516 of New Scientist magazine, 10 September 2005, page 12
No comments yet.