Serial killer Angus Sinclair is seeking to have his record Scottish prison sentence of 37 years for the World' End murders cut after claiming the judge who jailed him fell into error.

Sinclair also maintains that the minimum term imposed on him as he was jailed for life for the killings of 17-year-olds Helen Scott and Christine Eadie in October 1977 was excessive when compared to other terrible cases of murder.

The victims were last seen by police on patrol outside the World's End pub in Edinburgh's High Street.. Miss Eadie's body was found the next day at Gosford Bay, Aberlady, in East Lothian.

Miss Scott was found dead, naked from the waist down at a field near Haddington about five miles away.

Sinclair's counsel Ian Duguid QC told judges at the Court of Criminal Appeal in Edinburgh that the 37-year tariff imposed on Sinclair, 70, by Lord Matthews was "somewhat symbolic" because it was 37 years between the offences and his conviction last year.

He said the chances of Sinclair being around to have his case for release considered by the parole board were "negligible".

The convicted murderer and rapist was the first person to be prosecuted following new double jeopardy legislation after he was previously acquitted of the rape and murder of the teenagers at a trial at the High Court in Edinburgh in 2007 on a no case to answer submission. He was charged with committing them with his brother-in-law Gordon Hamilton who died in 1996.

Judges cleared the way for a fresh trial after ruling it was highly likely that a reasonable jury would have convicted on new evidence over advances in DNA and evidence from the previous trial.

Sinclair was ordered to be detained in 1961 as a 16-year-old for the culpable homicide of an eight year-old girl. In 1982 he was given a life sentence for rapes and indecency offences against girls.

He was given a further life sentence in 2001 for the 1978 murder of 17-year-old Mary Gallacher who was sexually assaulted in Glasgow.

The Crown had included information on the life sentences previously imposed on Sinclair as documentary productions in the indictment for Sinclair's trial over the World's End murders.

The defence counsel argued that in looking at Sinclair's convictions after the World's End murders the sentencing judge had taken into account "an inappropriate consideration".

Legislation passed by the Holyrood Parliament allowed that for offences after 2011 but it had not been backdated to cover cases before then.

Mr Duguid said: "This case does not fall into this category because that piece of legislation does not provide for backdating, but that is the law."

"The fact of the matter here is that the trial judge was wrong to take account of these features because the statutory provisions to which he referred did not allow him to do that in this case," he said.

He told Lady Paton, sitting with Lady Clark of Calton and Lord Malcolm, that they should look afresh at the minimum term imposed on Sinclair because of what he maintained was an error on the part of Lord Matthews.

Mr Duguid also pointed out that serial killer Peter Tobin, 69, had been given a 30-year minimum term for the murder of Vicky Hamilton, 15, after his earlier conviction for the slaying Angelika Kluk.

The senior counsel said that double murderer Thomas Smith (31) had received 32 years following the killing and sexual assault of Diane Fallon (43) and her 10-year-old daughter Holly in Cronberry, in Ayrshire.

Lord Advocate Frank Mulholland QC said the Crown had taken the steps it did to provide information on Sinclair's crimes and convictions because it was "highly relevant" for the court.

Sinclair dropped attempts to appeal against his conviction previously.

Lady Paton said the appeal judges would reserve their judgement but hoped a decision would not take too long.