But for the scrapping of the 800-year-old double jeopardy principle - that people cannot be tried twice for the same crime - Billy Dunlop would have literally got away with murder.

He killed his 22-year-old former partner, Julie Hogg, in a frenzied sex attack in 1989, then lied his way through two trials to escape being jailed for life.

His case is the first to succeed under new laws that allow people convicted of the most serious offences to be re-tried, where there is "new and compelling" evidence. No others are currently in the pipeline but prosecuting authorities expect the case to prompt others now to come forward.

Dunlop was always considered the prime suspect, as his hair and sweater fibres were found on her body, and traces of his semen were detected on the towel in which her body was wrapped.

But twice a jury at Newcastle Crown Court failed to reach a verdict and after the second hearing in October 1991, the labourer was formally cleared.

In 1998 he was jailed for seven years for another savage attack, and he later told a female prison officer he had killed Ms Hogg.

The Crown Prosecution Service took the unusual decision to try him for perjury, as he had lied on oath during the murder trials.

He was sentenced to serve six years after admitting two counts of perjury at Teesside Crown Court in 2000, to follow on from the seven-year sentence he was already serving for the vicious attack, whose victim was also a former lover.

Yesterday he became the first killer to be convicted under the new legislation which aims to prevent serious offenders escaping justice.

The change to the double jeopardy rule, which applies to offences carrying a maximum sentence of life imprisonment - chiefly murder, manslaughter and rape - came into force in April last year under the Criminal Justice Act 2003..

The offences must also be those for which the consequences to the victim or society at large are particularly serious.

It was amended to shore up public confidence in the legal system, just as forensic advances in the use of DNA were allowing detectives to revisit old, unsolved cases to find new, incriminating evidence.

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• He stole my son, now I’m alone in hell
• Back on the air, but don’t mention Mugabe
• Ten kitchen gadget gift ideas