The two young women Angus Sinclair was accused of murdering after an encounter at the World's End pub had been childhood friends.
Helen and Christine were seen talking to two men in the pub
Helen Scott and Christine Eadie were both aged 17 when they were raped and murdered.
The High Court in Edinburgh heard how the girls, who enjoyed going out together, were last seen alive at the World's End pub in the city.
A judge has thrown out the case against Sinclair, citing insufficient evidence.
Helen and Christine met at Firrhill High School in Edinburgh, and were fans of 1970s teen pop stars Donny Osmond and David Cassidy.
Friends said Christine was the more outgoing of the pair and lived with her grandmother during most her childhood.
She took a job as a typist in a surveyor's office in Edinburgh when she finished school.
Helen was very close to her parents and did not go out as often as her friend.
Helen's father Morain, 77, who was in court each day of the trial, said her mother Margaret died 12 years after her daughter's murder. He said she never recovered from the grief.
Helen had worked at a kilt makers in Princes Street and went straight from work to meet Christine on Saturday, 15 October, 1977.
Christine was wearing a denim jump-suit and wool coat with fur collar, while her friend wore a new black coat with Burberry lining which she had bought just days before.
The girls met up with two friends - Christine's flatmate Toni Wale and Jacqueline Ingles - and the four went to a number of pubs.
The group arrived at the busy World's End pub at about 2200 BST
The World's End pub was busy on the night in question
Helen and Christine sat in the crowded bar drinking whisky, while Toni and Jackie spoke to a friend in another part of the pub.
When they were there, the girls were invited to a party in Portobello with a friend of Toni's, but declined the invitation.
Drinkers later said they remembered the girls talking to two men, one who had a "brooding presence".
Helen and Christine left the pub just before closing at 2300 BST.
One of the girls, believed to be Helen, was said to be drunk and fell over in the street.
A policeman on the beat picked her up and then watched her go down the street with a "shifty-eyed" man who had been standing nearby.
That was the last time the two women were seen alive by anyone except their killers.
At about 1400 BST the next day, two dog walkers found Christine's body at high water mark at Gosford Bay, Aberlady, in East Lothian.
Her naked body was found face up, 10ft feet from the water. Christine had been bound and gagged with her tights and underwear.
The young woman had been badly beaten, sexually assaulted, and had died from strangulation.
A necklace and rings had been stolen from her and neither they, nor the rest of her clothing, were ever recovered.
Footprints were found in the sand nearby and one in particular was a size eight or nine boot with a ribbed patterned sole.
Some items of the victims' clothing were never found
Police who were examining the scene received a call at about 1800 BST to say that a second body had been found seven miles away in a field by the Huntingdon to Coates road, near Haddington.
A farm worker saw what he thought was a mannequin but it was Helen Scott's body.
Helen's body lay face down, and was naked from the waist down, partially covered by her new coat.
Her tights and belt had been used to tie her up and while she had not been gagged, her underwear was found near her face.
Again, other items of clothing were missing but her coat played a key role in the inquiry.
Like her friend, Helen had been badly beaten, sexually assaulted and her head had been stamped on, leaving a pattern which resembled the boot print found on the beach near to Christine's body.