In 1984 Dr Alec Jeffreys made an unexpected discovery whilst working on the origins of the gene for myoglobin at his facility in Leicester. Taking blood samples from his colleagues and himself, he chopped up the genetic material with an enzyme and separated the fragments according to how quickly an electric field stimulated them to move through jelly. Tagging them with a radioactive strand of DNA, the result was what seemed to be a bar code unique to every individual.
Jeffreys had discovered the DNA fingerprint, which only seemed similar in identical twins. Soon realising he had a new form of identification method, he used the process to prove paternity cases, his first success being a black teenager who had been refused admission to the UK to join his mother as blood tests could not confirm parentage. Jeffreys proved who he was and he was allowed to enter the country.
The British police adopted DNA fingerprinting in 1986, as it was clear that most crime scenes contained fragments of DNA left by the perpetrator. Jeffreys' first success in criminal detection came in 1987 when a second teenager was raped and strangled in two years. Police convinced 4,600 men in the area to give blood samples. The killer was one Colin Pitchfork, who at first evaded the blood test but was later tested and convicted.
In America the FBI adopted DNA fingerprinting in 1988, but it was soon to be used as a means of proving innocence in miscarriages of justice as well as finding the guilty. For instance, an Oklahoma jury found Robert Lee Miller Jr guilty of raping and murdering two elderly women in 1988. Ten years later, DNA in a semen sample was shown not to be Miller's but that of another convicted rapist.
DNA fingerprinting has revolutionised criminal detection, but can have several drawbacks. First of all, too much reliance on the technique could well lead to a decline in the abilities of detectives to catch criminals in other ways. And secondly, DNA fingerprinting is only of use if you already have a sample of the perpetrator's DNA on file. National criminal DNA databases are being set up to record DNA from every person who has been in trouble with the law. But there is a natural urge for governments to have a complete database of the population. Whilst this would undoubtedly assist crime clear-up rates, it has profound problems for liberty and freedom.
(c) Anthony North, Feb 2007