A COLD-BLOODED killer who murdered his adoptive parents after the family moved from the North-East to Australia has been jailed for 28 years.

The jailing of David Weightman brings to an end a family's six-year crusade for justice, after Australian authorities initially dismissed the double death as an accident.

Pam and Bill Weightman were drugged and strangled by their son, who then tried to cover up the killing by pushing their car 60ft over a ravine. He was finally caught when forensic tests uncovered bruising that proved the couple had fought desperately to stay alive.

Last night, Mrs Weightman's sister, Mary Scott, 52, of Birtley, near Chester-le-Street, County Durham, said the sentence should have been life.

She said: "It is shocking. We thought it would have been more. The most he will probably serve is 22 years as he is not eligible for parole until he has been in prison for 24 years, but he has already served two years on remand.

"It is a hefty sentence, but I do not think it is enough. He will be younger than me when he comes out."

Reporters in Australia have been banned from identifying Weightman as the hunt continues for an accomplice.

Australian Supreme Court judge Justice Peter Hidden jailed the 25-year-old for life, with a recommendation he serve 28 years, after Weightman changed his plea to guilty on the eve of the double murder trial.

Justice Hidden said that initially a post-mortem examination concluded the deaths were accidental, but that it was only after the couple's relatives expressed concern that a forensic pathologist said he could not exclude murder.

A second examination confirmed Mr Weightman, 51, had suffered throat injuries "typical of strangulation" while Mrs Weightman, 50, suffered bruising suggesting she had been forcibly moved.

Sedatives were also detected in their blood.

Family members sobbed in court as Justice Hidden said the couple had struggled for their lives.

David Weightman was only three months old when he was adopted by Mr and Mrs Weightman, who lived at Birtley.

During the 1980s, Mr Weightman lost his job as a foreman at the Royal Ordnance factory in the town and the family moved to Australia to build a new life in the suburbs of Sydney.

The couple opened a successful kindergarten, but on January 9, 2000, their bodies were found by a park ranger in the wreckage of their car at the bottom of a cliff bordering a winding bushland road leading to the coast.

It was only after a sustained campaign by the couple's relatives in Australia, including Mrs Weightman's Gateshead-born sister Meg Urwin, 53, and her husband Alan, that the case was reopened.