A jury found Pawel Rodak guilty by majority verdict yesterday of killing Roger Gray.
Mr Gray, 64, who had retired as a lecturer at Heriott-Watt University, Edinburgh, died from blood loss in his home in Merchiston Crescent in March 2011.
The High Court in Livingston was shown an eight-inch kitchen knife thought to be the murder weapon. The jury was told after the attack Rodak wrecked Mr Gray’s flat.
Rodak, 20, told psychiatrists he carried out the attack because he felt “uncomfortable” at being asked to engage in sadomasochistic sex.
He refused to instruct defence counsel at the start of the 13-day trial and offered to plead guilty to murder.
The Crown rejected the plea on the grounds that Rodak had a psychiatric history which suggested he may have had diminished responsibility at the time of the killing.
In an unusual move, temporary judge Michael O’Grady appointed Donald McLeod QC as “amicus curiae” – a friend of the court – to represent Rodak, who was found guilty of the lesser charge of culpable homicide on the grounds of reduced responsibility.
An allegation he tried to defeat the ends of justice by concealing clothing at the flat, disposing of items from the murder scene, and endangering life by leaving a lit candle near escaping gas in the flat was dropped by the Crown.
During the trial, which was subject to reporting restrictions, the jury heard evidence that Rodak had advertised on the “Gay Romeo” website.
He told psychiatrists he had decided to become a male prostitute because he had no money.
He said his first sexual experience had been at the age of 15 when he was assaulted by a 26-year-old man in Poland. He said his attacker held him down, banged his head on the floor and raped him “like an animal”.
He claimed Mr Gray had offered to double his fee if he inflicted pain on him with a “cat o’ nine tails” whip and had slapped him on the face.
Consultant psychiatrist Dr Fionnbar Lenihan, 45, said: “Mr Rodak went to the kitchen to get his jacket and leave. Mr Gray followed him and became angry.
“He said Mr Gray pushed him and hit him again and said: ‘I’m paying you’. Mr Rodak then picked up a knife from a table and said: ‘I go wild you know’.
“When I asked him what was going through his mind he said: ‘I felt angry and frightened’.”
Dr Lenihan said the rape – about which Rodak still has flashbacks – led him to diagnose post traumatic stress disorder.
Mr Gray’s friend, retired consultant physician Sandy McMillan, 65, said his friend “liked Eastern European men”.
Charles Coventry, 78 – who lives in the flat above Mr Gray’s – told how he smelled gas early on Saturday 19 March, 2011. He called police, who found Mr Gray lying dead in a pool of blood in his hall in his pants. Gay porn videos and DVDs were scattered around the flat along with knives and a whip.
Mr Gray was a lecturer in actuarial mathematics and statistics at Heriot-Watt, where he lectured for 40 years before retirement in September 2007.
Mr Gray’s brother Fred, 67, said: “There is nothing that can bring my brother back. His killer will have plenty of time to reflect on his actions, and will hopefully devote the next phase of his life to make himself a better person fit to contribute to society.
“Our family will never forget Roger, who helped many people during his life.”