IT is the kind of police science that features so heavily in TV crime series and Hollywood films, but DNA evidence has had a big impact throughout the Avon and Somerset force and even in Bridgwater.

Far away from the glamorous actors and actresses of CSI, this year the Criminal Investigations Department is celebrating the 20th anniversary of the first successful conviction from DNA evidence in the world.

It happened at Bristol Crown Court on November 13, 1987, when Robert Melias pleaded guilty to rape and was jailed for eight years for his attack on a 42-year-old disabled woman.

Since then, DNA evidence gathering has advanced beyond recognition - and now, profiles secured decades earlier, are being used to successfully prosecute offenders who had previously escaped justice.

Closer to home the expensive technique was used this year in a Bridgwater case to track down the town rapist responsible for a horrific sexual attack on a mum-of-two back in April 25,1993.

Geoffrey Godfrey appeared before Bristol Crown Court on October 15 this year and pleaded guilty to the rape, and other sexual offences.

It was the first time familial evidence had been used to successfully prosecute a historic cold case rape and saw Godfrey jailed for six years.

A review of the investigation into the 1993 assault started in 2005 and details of over 4,000 potential matches had to be processed and eliminated to produce a "one in a billion" match.

See the Mercury on Tuesday for our special feature.