How a cigarette helped solve a 30-year-old murder
A cigarette stub recovered from Mary McLaughlin's flat provided the first clue to her killer's identity - more than 30 years after she was strangled.
A matching DNA profile was later discovered hidden in the knot of the dressing gown cord used to murder the mother-of-11.
Senior forensic scientist Joanne Cochrane was working at the Scottish Crime Campus in Gartcosh, North Lanarkshire, when she was asked to review evidence from the scene that had been preserved in paper bags for 30 years.
"They didn't know about DNA profiling at that time," she said. "They didn't know the potential held in these items."
"They couldn't possibly have known the value that it might have had."
The breakthrough initially baffled cold case detectives as the prime suspect was a prisoner in Edinburgh when Mary, 58, was found dead in the west end of Glasgow.
But a governor's log book confirmed serial sex offender Graham McGill was on parole when the grandmother was killed.
And it revealed he returned to his cell within hours of leaving Mary's home in the early hours of 27 September 1984.
