genetic fingerprinting

Technique developed in the UK by Professor Alec Jeffreys (1950- ), and now allowed as a means of legal identification. It determines the pattern of certain parts of the genetic material DNA that is unique to each individual. Like conventional fingerprinting, it can accurately distinguish humans from one another, with the exception of identical siblings from multiple births. It can be applied to as little material as a single cell.

Genetic fingerprinting involves isolating DNA from cells, then comparing and contrasting the sequences of component chemicals between individuals. The DNA pattern can be ascertained from a sample of skin, hair, blood, or semen. Although differences are minimal (only 0.1% between unrelated people), certain regions of DNA, known as hypervariable regions, are unique to individuals.

Genetic fingerprinting was first allowed as a means of legal identification at a court in Britain 1987. It is used in paternity testing (from 1988), forensic medicine, and inbreeding studies. The world's first national DNA database began operating in the UK April 1995.

In the USA the FBI have been collecting samples since 1993. In many thousands of court cases the results of DNA tests have been accepted as evidence, although several courts have challenged the validity of conventional genetic fingerprinting. A new method that makes it possible to express genetic information about an individual in digital code means that genetic fingerprinting will now be much more accurate than before.

In 1993 a positive identification was made of the remains of a US soldier who had died in Vietnam 29 years before. Subsequently the US Defense Department launched a screening programme, tracking tissue samples from military personnel for possible use in identification. In September 2000, a man in California was charged with rape after what is believed to be the first US case of a criminal arrest based entirely on DNA evidence.

In August 2001, the US Justice Department announced that it would provide more than US$30 million to state crime laboratories to analyse DNA from criminals or from crime scenes. It was intended to help clear a backlog of some 500,000 samples not yet analysed. The DNA would then be added to the FBI's national DNA computer database to solve crimes. By 2001, the FBI database had DNA profiles of about 500,000 convicted criminals.