A chef has been jailed over the "cold blooded" rape of a teenage girl after he was caught by DNA evidence six years after the attack.

John Morton, 32, pinned the 17-year-old to the ground and threatened her with a knife during the crime. Morton walked free for six years after the sickening sexual assault on July 28, 2002 in Trafalgar Street, Clydebank before he was caught.

Police stumbled on his secret past after investigating a domestic disturbance last May and taking his DNA, before matching it to the rapist.

Morton, of Claymore Drive, Houston, admitted rape at Glasgow High Court last month and at the High Court in Livingston on Thursday he was jailed for six years and put on the sex offenders register for life.

The court heard how Morton struggled with the frightened girl, put his arm over her mouth and threatened to stab her. A security light then came on and, while Morton attempted to switch it off, the victim tried to escape.

He then pushed her, pulled down her trousers and raped her. Morton then got up, jumped over a fence and ran off.

The distraught victim was soon discovered by a policeman who had been dealing with a pub break-in. She told the officer: "I have been attacked."

In May last year, Morton was questioned over an alleged breach of the peace offence. He provided a swab and the DNA on it matched that taken from the rape incident.

Morton was later questioned about the attack and denied knowing where Trafalgar Street was before later pleading guilty.

On Thursday, Judge Lord Brailsford said: "This was the cold blooded rape of a very young girl, a 17-year-old girl of whom you had no knowledge. The court has to take the most stringent view of this matter in the public interest.

Lord Brailsford said he reduced this sentence to six years because of Morton's guilty plea.