SERIAL killer Steven Grieveson was gang raped in his youth and made money by being a rent-boy, a court has heard.
Jurors were given an insight into the early life of the quadruple killer during his trial over the death of schoolboy Simon Martin.
Grieveson, 42, is serving three life sentences for the murders of David Hanson, 15, Thomas Kelly, 18 and David Grieff, 15, in Sunderland in the early 1990s.
He admits killing 14-year-old Simon in 1990 but denies murder on the grounds of diminished responsibility.
Professor Derek Perkins told the court Grieveson has “psychopathic traits” to his personality which, mixed with vulnerabilities, makes for a “dangerous combination”.
He added: “His lack of emotion, callousness, lack of remorse are elements that would have contributed to his ability to kill, more than once.”
Old social services records show Grieveson was taken into care when he was 13 and lived at a school in Cumbria.
Reports from the time describe Grieveson as having “no insight into his behaviour or trouble he causes” and describe him as an “emotionless boy”.
The professor told jurors how he performed a series of psychological tests on the killer and had discussions with him about his early life and growing up.
It was during their meetings that Grieveson said he had been sexually abused as a boy, gang-raped and carried out sexual favours for older men in exchange for cash.
Professor Perkins said: “He described during interview something which he regarded as a very traumatic, life-changing event for him.
“He had contact with one of those men and was taken to a property where he was in effect raped by three men.
“He described this as something that really affected him in a very bad way at the time.
“He felt it subsequently shaped some of his behaviour and thinking.”
The professor said Grieveson had described being sexually abused by an older male when he was as a child and that the mistreatment went on for “some time”.
Professor Perkins added: “He spoke about sniffing glue every day and of getting into a pattern of behaviour where, as he put it, he prostituted himself to older men by masturbating them, doing this for money.
“He spoke at the time of describing this of feeling he wanted to exploit these older men, partly for money, partly because there was satisfaction in exploiting these men who were involved in sexual activity with him.”
The professor said Grieveson became “irritated” when talking about the four killings, which he said were accidents which happened while trying to frighten his victims, but was a “very co-operative patient” otherwise.
Professor Perkins said: “I was struck by the emotionlessness of his descriptions of these events. There seemed to be a themed lack of emotion about traumatic or violent events.”
Grieveson denies murder.