Serial killer and rapist Angus Sinclair, who died in prison last week, was a key suspect in Carol Lannen’s death – known as one of the Templeton Woods murders.
Sinclair died in HMP Glenochil, Alloa, on March 11 aged 73.
He had been convicted in 2014 for the 1977 World’s End murders.
Sinclair spent more than half his life behind bars for killing four girls, as well as for a string of sex attacks on young children.
But detectives suspect he could have been behind several unsolved murders from the 1970s.
In 2014 Sinclair’s case made legal history when he was jailed for a minimum of 37 years for the murder of two teenage girls four decades before.
He was found guilty of the rape and murder of teenagers Christine Eadie and Helen Scott, who were last seen in Edinburgh old town’s World’s End pub.
The pair had been bound and strangled with their underwear. Their bodies were discovered the following day in East Lothian.
The sentence was the longest handed out in Scottish legal history.
Judges described Sinclair’s murders as displaying “an immeasurable capacity for evil, depravity, and sadism”.
In 1961, in Glasgow, he strangled Catherine Reehill, 7, then dumped her body on a tenement stairway.
He was also convicted of the 1978 murder of Mary Gallacher, 17, who was raped and stabbed near a railway line in Glasgow as she went to meet a friend.
His involvement in Carol’s murder was dismissed after police became aware he was in prison at the time.
Was another man known as ‘The Zodiac Killer’ to blame?
The Zodiac Killer is believed to have murdered five people in his reign of terror in Northern California between 1968-1974.
However, in a series of coded letters to newspapers, the Zodiac Killer himself claimed to have killed as many as 37 people.
Police however, only linked five murders — and two other injuries — to him.
A dossier passed to police in Tayside said the killer had fled to Scotland.
It claimed that the “Zodiac’s last act” was the murder of Carol Lannen.
Although the Tayside investigation was stood down after six months, the suspect — who has links to Texas, Los Angeles and Tennessee — remained “under review”.
Although survivors said the Zodiac had an American accent, it was suggested he could have spent time in Britain through service in the US military.
Others have claimed the Zodiac “gunsight” symbol is actually a Celtic cross and suggested the killer could have had Scottish heritage.
The killer used the name “Zodiac” in a series of taunting letters sent to the local Bay Area press.
These letters included four ciphers. Only one has been definitively solved.
In 2007, the story was turned into a hit film, Zodiac, starring Robert Downey Jr, Jake Gyllenhaal and Brian Cox.