A bungling opportunist whose trail led police to Karen's body
Alexander Pacteau was no criminal mastermind.
He was a bungling opportunist who seized on a vulnerable Karen Buckley when he met her outside Glasgow's Sanctuary nightclub on the night of April 12.
Glasgow detectives were utterly baffled by Pacteau's error-ridden attempts to cover his tracks.
They were also taken aback by the callous disregard Pacteau showed for the Irish nurse in his attempt to dissolve her body.
The details of his sickening crime emerged in court.
It has not been explained what transpired between Pacteau and Karen outside the club that night.
CCTV footage showed them walking together towards his parked car, with subsequent footage showing them travelling east.
In the 12 minutes and 46 seconds in which Pacteau pulled his car in off the road at Kelvin Way, he had taken Karen's life by smashing her on the head with a spanner up to 13 times.
Such was the violence of the attack that the imprint of the spanner head was left on Karen's skull.
Pacteau claimed he was heavily intoxicated and lost his temper after Karen passed a trivial comment .
For a time, he drove around Glasgow with her body in the passenger seat before taking her back to his flat on Dorchester Avenue.
Pacteau first tried to dissolve Karen's naked body in the bath.
Incredibly, his flatmate - who knew nothing of what had happened - had had his mother staying at the flat, but they were away on a hill-walking trip
Pacteau rang the young man on his mobile phone to check how long he would be away from the flat before he began researching the chemical properties of caustic soda on his smartphone.
He also asked a Tesco worker to recommend a cleaning product to remove blood from a mattress.
His flatmate arrived back from the trip to discover him cleaning the flat and the corridor.
Pacteau was also caught on CCTV buying a 220-litre blue plastic barrel in a hardware store. This would prove central to the investigation.
He later placed Karen's body inside the barrel, filling it with caustic soda and drain unblocking fluid and storing it at an isolated Glasgow hill farm.
The first clue for detectives was the CCTV footage of Pac- teau talking to Karen outside the nightclub.
Police called to his flat three hours after he had placed the barrel containing Karen's body at the farm. The smell of bleach made them immediately suspicious.
When confronted, Pacteau said: "I was just calling to see you."
Suspicious items were found in his bedroom, including parcel tape, a tool box and nail brushes.
Initially, Pacteau claimed Karen had cut her head on the bed frame during consensual sex.
He first insisted she had left his flat to walk home at 4am. Later, he claimed he hit her with the spanner in self-defence.
Police now describe all of those claims as "total lies and nonsense".
Det Insp Jim Kerr said police were satisfied Pacteau left the nightclub to deliberately prey on women.
If it had not been Karen, it would have been another girl, he said.
Pacteau has a previous conviction for forgery linked to photo- copying sterling banknotes.
Separately, he was acquitted of a sexual assault charge after he was accused of attacking a woman on November 27, 2011.
While police have said there was absolutely no evidence that Karen was sexually assaulted, the alleged 2011 incident bears remarkable similarities to the attack on the young Irish woman.
The complainant said it happened late at night as she was walking home alone.
She claimed Pacteau grabbed her, placed his hand on her mouth and sexually assaulted her.
Pacteau denied the claims, and a Glasgow High Court jury believed him, acquitting him of the sexual assault charge by a majority verdict in February 2013.