Keith Eynon, 68, was the head of Strathclyde Police's Forensic Support Unit when he was called to a lane off Ard-gowan Street, Greenock, in June 1986.
Yesterday, a jury at the High Court in Edinburgh heard how a clump of hair was recovered close to where the 16-year-old's body was found on June 2 that year.
The court heard how Mr Eynon helped gather forensic evidence from the scene.
Mr Eynon told prosecution lawyer John Scullion: "Certainly the clump of hair suggests a struggle." He was giving evidence for the second day at proceedings against 49-year-old John Docherty.
Docherty, of Dunoon, Argyll, denies murdering jeweller's assistant Elaine.
He claims that at the time he is alleged to have stripped and strangled her, he was at home with his parents, who are no longer alive.
Docherty has also lodged a special defence of incrimin-ation, claiming the culprit might be among a list of 41 names taken from files of the police investigation into the alleged murder.
Mr Docherty faces a charge which alleges that on June 2, 1986, in a lane near Ardgowan Street, Greenock, he seized Elaine by the hair, struck her on the head and either removed or compelled her to remove her clothing.
The charge goes on to allege that Docherty forced Elaine to the ground, pushed her face to the ground, sat or knelt on the teenager then placed a ligature round her neck and strangled her.
Docherty also denies stealing a handbag from Ardgowan Street on the same date.
He also denies a further charge of attacking another woman, Linda Hargie, on various occasions between 1990 and 1995 at an address in Ann Street, Greenock, by seizing her and pushing her on the head.
The trial, which is being heard before Lord Stewart, continues.