The advance of science means crimes will catch up with killers

was finally traced inside the knot of a dressing gown cord 30 years after he used it to strangle Mary Mclaughlin.

Forensic scientists persisted with a string of reviews into the 1984 murder of Mary as advances in science with the passage of time opened up opportunities not previously available to them.

After scientific examinations at the time of the murder proved inconclusive, cold case reviews to try to obtain DNA samples were carried out in 1999, 2002 and 2006. It was only after a fifth attempt began in 2014 that forensic scientists Joanne Cochrane and Nighean Stevenson finally located what was to prove a sample of Mcgill’s DNA.

At the High Court in Glasgow last week, Cochrane told prosecutor Alex Prentice QC: “We felt that the inside of the knot might be protected from contamination. We felt there was a possibility of receiving DNA from there. We did it very slowly and took photographs at all stages. It was very difficult to unfasten.” Cochrane said the latest analysis found a mixed DNA profile with a major profile attributed to Mary and a minor one to Mcgill. She told jurors that the likelihood of the DNA belonging to someone other than Mcgill was 85,000 to one.

The chance of DNA on a cigarette butt found nearby and on Mary’s dress not being from Mcgill was one billion to one and for the bra it was 320 to one. Prentice, who described the evidence inside the knot as like “a time capsule” back to 1984, asked: “Has DNA analysis greater opportunities now?” Cochrane replied: “Yes, as new technology comes on, we now have the gold standard of DNA profiling.”