A forensic scientist has told a murder trial that samples from 1977 were preserved in a "very good condition" when he came to analyse them for DNA.

Andrew Davidson, 46, said he believed scenes of crime work following the discovery of Christine Eadie and Helen Scott's bodies had been well-handled.

Mr Davidson, a forensic scientist with 22 years' experience, told how he carried out more than 18 months' work on the samples.

He is the last witness to give evidence for the prosecution in the trial of 69-year-old Angus Sinclair.

Mr Sinclair has been on trial at the High Court in Livingston for four weeks, where he denies raping and murdering the girls 37 years ago. He is accused of carrying out the attacks along with his late brother-in-law Gordon Hamilton.

Christine and Helen, both 17, were last seen at the World's End pub in Edinburgh on October 15, 1977. Their bodies were discovered in East Lothian the next day.

Mr Davidson, who works for the Chorley-based organisation Cellmark, carried out DNA analysis on items of clothing found on the bodies of the girls.

Among the findings was the conclusion that DNA evidence provides "extremely strong support for the view that Gordon Hamilton and/or Angus Sinclair were involved in the restraining and strangling of both Helen Scott and Christine Eadie, rather than an unknown and undetected individual or individuals".

Mr Sinclair has lodged three special defences - of consent to sexual intercourse, alibi and incrimination, blaming Hamilton.

Mr Davidson said he was not told of those special defences when he compiled his report in May this year.

He will continue giving evidence next week. The trial, before Lord Matthews, continues on Monday.