Rurik Jutting, a 31-year-old Cambridge graduate, has pleaded not guilty to murder but guilty to manslaughter on the grounds of diminished responsibility. The prosecution rejected the lesser plea.
Jutting is accused of murdering Sumarti Ningsih, 23, and Seneng Mujiasih, 26, two years ago, slashing their throats after saying he would pay them for sex.
He tortured Ningsih inside his apartment for three days before killing her and stuffing her body in a suitcase found on his balcony.
As the trial entered its second week, the defence said Jutting suffered from narcissistic personality disorder and sexual sadism disorder, as well as heavy use of cocaine and alcohol.
He had also experienced bouts of depression and suicidal thoughts, the court heard.
Forensic psychiatrist Richard Latham, called as a defence witness, said Jutting had told him he was abused at renowned English private school Winchester College.
A report from Latham read out in court said a boy had forced Jutting to perform oral sex on him at school.
"He described it in a way that he was a victim of sexual assault," Latham said.
Latham said people with narcissistic personality disorder had problems empathising with others and sought constant praise.
"When that breaks down the consequence is dramatic," Latham told the court.
Latham also said Jutting had described how he had become increasingly interested in torture, "culminating in dramatic and horrific acts".
His disorders mixed with the consumption of cocaine and alcohol had affected his behaviour, said Latham.
"At the time of the killings his ability to control his behaviour was substantially impaired," the psychiatrist said.
When asked by judge Michael Stuart-Moore whether voluntary intoxication constituted a defence, Latham said the drive to take drugs and alcohol was "extremely difficult to resist".
