A soil expert has told how she helped catch the killer of Irish student Karen Buckley because dirt on his car had been missed when he had it cleaned.
Alexander Pacteau was jailed for life in 2015 for brutally murdering 24-year-old Karen after meeting her at a Glasgow nightclub. The former private schoolboy, then 21, took Karen to his car where he strangled her and repeatedly hit her on the head with a foot-long wrench.
He carried her body into his flat in Kelvindale and tried to dissolve her body in a bath of caustic soda before dumping her remains in a barrel at a farm near Milngavie, East Dunbartonshire. Pacteau had his car professionally cleaned by a valet service after the killing in a bid to destroy evidence.
But Professor Lorna Dawson told how some soil which remained on the car's tyres proved crucial in the case. Her analysis of the soil proved the car had been at Dawsholm Park in Glasgow where Karen's handbag was dumped. Analysis of dirt found on Pacteau's boots also showed he had recently been at the farm.
Faced with the damning forensic evidence, Pacteau confessed to Karen's murder.
Speaking on BBC series Expert Witness, Professor Dawson, head of soil forensics at the James Hutton Institute in Aberdeen, said: "The car was very clean but when we looked underneath it, we were able to recover some material. When we looked at the car tyres we saw there was a band of soil which had avoided being washed off by the car wash procedure.
"We showed that profile was very similar with the turning point at Dawsholm Park. This was quite important because it took that vehicle nearby the bin at the entrance to Dawsholm Park where Karen's handbag was found. The soil evidence linked him to where Karen was found and to Dawsholm Park."
She added: "I'm very proud that we were able to help in this particular case. The physical evidence of the soil and the vegetation had done its job because it had helped Pacteau admit to killing Karen."
On the programme, an Irish charity who supported Karen's family throughout their ordeal thanked Professor Dawson for her work on the case.
Sally Hanlon, director of Support After Crime Services, said: "Due to the excellent work of Lorna Dawson he decided to plead guilty. If that forensic evidence wasn't available maybe there wouldn't have been such a quick outcome or a conviction.
"Murder trials are very difficult for families of the deceased. His early guilty plea was a benefit to the family."
Pacteau admitted murdering Karen and hiding her body and was ordered to serve a minimum of 23 years at the High Court in Glasgow in September 2015. Judge Lady Rae described the case as "shocking and disturbing" and said she found it "extremely difficult" to find words to describe what he did to Karen.
Karen, who was from Cork, was a nurse and had moved to Glasgow in February 2015 to study occupational therapy at Glasgow Caledonian University. The Expert Witness episode featuring the case is available on BBC iPlayer.
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