It happened on the A1 near Dunbar.
Underwear DNA 'Linked To Accused'
A trial has heard details of DNA found on a teenager's underwear linked to the man accused of her murder.
Jurors have already been told that Angus Sinclair claims Helen Scott and Christine Eadie, both 17, were "alive and unharmed'' when he left their company.
The girls were last seen at the World's End pub in Edinburgh on October 15 1977.
Christine's body was found the following afternoon at Gosford Bay in Aberlady, East Lothian, while Helen's body was discovered a few hours later in a wheat field near Haddington.
Sinclair, 69, is on trial at the High Court in Livingston where he denies raping and murdering the girls.
He is accused of carrying out the attacks along with his brother-in-law, Gordon Hamilton, who is now dead.
Earlier this week jurors heard Sinclair's version of events, described as his "recollection'', when a section of a defence report was read to the court.
It stated he had "consensual sexual intercourse'' with Christine followed by Helen, and that Hamilton had "sex with both girls in the opposite order''.
Sinclair then claims that Hamilton drove him back to East Lothian as he wanted to continue fishing. He said the girls were "alive and unharmed'' when he left.
The report was read out during the evidence of forensic scientist Geraldine Davidson, who works with English-based company Cellmark.
During her third day of giving evidence, she talked through DNA analysis carried out on pants found beside Helen's head when her body was discovered.
One of the areas was on the outside front left hand side which revealed a mixed DNA profile. She said in her opinion Sinclair could have contributed to this profile.
The results were sent for further analysis and there was "extremely strong support'' found for both Sinclair and Hamilton to be contributors.
Ms Davidson was asked by Lord Advocate Frank Mulholland, prosecuting, to discuss her findings in relation to the gusset area.
She told the court that the absence of a significant amount of DNA evidence in that section did not fit with the underwear having been put back on and worn after sex.
Two days earlier, Ms Davidson previously talked the court through an analysis of DNA found on underwear used to gag Christine.
The findings could support the suggestion that the teenager had not put her underwear on after intercourse, the witness said.
Defence QC Ian Duguid has not yet had the opportunity to question her.
Sinclair denies the charges against him and has submitted three special defences: incrimination - blaming his brother-in-law; alibi - saying he was fishing on the banks of the Firth of Forth near Cockenzie power station at the time; and consent to sexual intercourse.
The trial before Lord Matthews resumes on Monday when Ms Davidson will continue giving evidence.
The 26 year old was first targeted in Briarscroft Road.
Euan Johnston was shot in his car last month.
The family of three crash victims took their case for the 59-year-old to be put on trial to the Appeal Court in Edinburgh earlier this year.
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