“I’ve seen many a thing, but never a couple courting in a graveyard!” a woman remarked to her husband as they drove past St. Mary’s Cemetery at Biggar, Lanarkshire, late in the evening of AUGUST 6th, 1967.

The next morning 15-year-old Linda Peacock was found strangled in the graveyard, and the woman and her husband realised they had witnessed a prelude to murder.

Linda had gone to a fair in the town, and a search had been launched for her when she failed to return home. She was found slumped against a gravestone, her skirt down, her breasts exposed, with a bite-mark visible on one of them.

Suspicion focused on a local boarding-school for maladjusted boys, but it seemed they were all in their dormitories at the time of the murder – 10.20 p.m. – when screams were heard by three witnesses.

When the boys at the school were questioned further and more intensively, the two room-mates of 17-year-old Gordon Hay admitted they were covering up for him. They said he had not been with them in the room between 9.55 and 10.45 p.m. as he claimed. They had gone to bed at 10.30, and he had come in breathless, dishevelled and agitated some 15 minutes later.

Hay denied he had left the building, but the tell-tale bite-mark on Linda’s breast proved he was lying. His teeth had a distinctive irregularity, and the bite-mark matched it to perfection.

His trial ended with the first murder conviction secured in Scotland on the evidence of a tooth-impression, and as he was under 18 at the time of the crime he was ordered to be detained during Her Majesty’s pleasure.