One of the keystones of forensic science is DNA testing. DNA (deoxyribonucleic acid) is the genetic material present in every cell. Each individual has a Unique DNA Profile. There are even a few differences between the DNA of identical twins.
A British scientist, Sir Alec Jeffreys, developed DNA profiling in the 1980s. DNA for profiling can be extracted from samples of human cells found at a Crime Scene, including blood, semen, skin, saliva, mucus, perspiration and the roots of hair, and Profiling can even be carried out on old and dried out samples.
The case of Colin Pitchfork was the first murder conviction based on DNA profiling evidence (there was a previous rape conviction based on this type of evidence).
After going missing, Lynda Mann, a 15-year-old schoolgirl, was raped and murdered in the grounds of Carlton Hayes psychiatric hospital in Narborough, Leicestershire, in November 1983. Forensic examination of semen sample showed that it was a type found in only 10% of men, and was from someone with type A blood. However, the police did not find a suspect.
In 1986, another 15-year-old schoolgirl, Dawn Ashworth, was similarly sexually assaulted and strangled in the nearby village of Enderby, and semen samples showed the same blood type.
Richard Buckland, a local 17-year-old with learning disabilities who worked at Carlton Hayes psychiatric hospital, had been spotted near Dawn Ashworth’s murder scene and knew unreleased details about the body. In 1986, he confessed to Dawn Ashworth’s murder but not Lynda Mann’s.
Using Sir Alec Jeffreys’ new technique, scientists compared the semen samples with a blood sample from Richard Buckland. This proved that both girls were murdered by the same man, and also proved that this man was not Richard Buckland – the first person to be exonerated using DNA.
In 1987, in the first ever mass DNA screen, the police and forensic scientists screened blood and saliva samples from 4,000 men aged between 17 and 34 who lived in the villages of Enderby, Narborough and nearby Littlethorpe and did not have an alibi for murders. The turn out rate was 98%, but the screen did not find any matches to the semen samples. The police and scientists expanded the screen to men with an alibi, but still did not find a match.
In August 1987, a woman overheard a colleague, Ian Kelly, boasting that he had given a sample posing as a friend of his, Colin Pitchfork. Pitchfork had persuaded Kelly to take the test as he claimed he had already given a sample for a friend who had a flashing conviction. The police arrested Colin Pitchfork in September 1987, and scientists found that his DNA profile matched that of the murderer.
Colin Pitchfork had previous convictions for flashing, and claimed that the murders had begun as flashings, but the girls had run away, which had excited him.
In January 1988, Colin Pitchfork was sentenced to life imprisonment for the murders, and was told he had to serve a minimum of 30 years.