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DNA Profiling and the Colin Pitchfork Case
DNA profiling has become such a fixture of forensic science that it's easy to forget that the process has been around only a little more than a decade. In 1987, when police in England were the first to apply the technique in a murder investigation, it was as revolutionary as the first use of fingerprints a century before.
In 1983, fifteen-year-old Lynda Mann was found raped and strangled in the village of Narborough. Nearly three years later, Dawn Ashworth, also fifteen, was found in the same condition in nearby Enderby. (Since the victims were found in the vicinity of a footpath called The Black Pad, some newspapers began to refer to the murderer as "The Black Pad Killer.") Police had long exhausted all leads in the case when Alec Jeffreys, a geneticist at the University of Leicester, announced the creation of the process of restriction fragment length polymorphism (RFLP). In short, given an adequate sample of any individual's DNA, Jeffreys could create that individual's unique "genetic fingerprint." The DNA sample could be isolated from a variety of body tissues: blood, saliva, hair, or - of particular interest to the police - semen.
Investigators in the Mann/Ashworth case decided to use Jeffreys' discovery in a daring approach to catching the killer: they would identify him using his own genetic code. First, semen found on the victims was used to create the DNA profile of the murderer. Then, all unalibied local men between the ages of 16 and 34 were requested to give authorities a DNA sample - drawn from their blood - to compare to the killer's. Naturally, police didn't think there was much chance that the murderer would willingly walk in and roll up his sleeve. To the contrary, they fully expected the guilty party to do his best to avoid the test . . . and that's exactly what happened.
In August of 1987, police finally got the case-cracking lead they'd been looking for.
A woman who worked in a local bakery told investigators that while drinking in a pub with some co-workers, one of them claimed he'd taken the blood test for another man. When police questioned the man, Ian Kelly, he admitted that he had, indeed, given a blood sample for another bakery employee named Colin Pitchfork. Pitchfork had convinced Kelly he couldn't take the test because he'd already helped out someone else - a friend with a police record for flashing - by giving a sample for him. Pitchfork claimed to be afraid that if he gave another sample he'd be arrested for the deception.
As it turned out, Pitchfork's reason for wanting Kelly to take the test for him was much less convoluted than that: he was the murderer. When police went to his home, Pitchfork readily admitted to killing both girls more or less because "they were there." Himself a convicted flasher, in each case Pitchfork exposed himself to his victim, then pursued her when she ran away. To him, it was the girls' fault that they died - they simply shouldn't have been there. On January 22, 1988, Pitchfork pleaded guilty in court and was given a life sentence. He thus became the first murderer caught because of DNA evidence.
Interestingly, this case is also the first in which a suspect was cleared because of DNA evidence. An emotionally disturbed young man who was at one point the prime suspect in the case (and, in fact, confessed to killing Dawn Ashworth) was set free because his DNA didn't match that found on the victims.
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DNA Fingerprint pioneer, Sir Alec Jeffreys |
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Colin Pitchfork, aka The Black Pad Killer |
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A DNA autoradiograph or "fingerprint." |
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