By Farah Master

HONG KONG (Reuters) - British investment banker Rurik Jutting acted rationally before and after he killed two Indonesian women in his luxury Hong Kong apartment and had even telephoned his mother after killing the second woman, the prosecution said on Wednesday.

Jutting, a former Bank of America Corp employee, has pleaded not guilty to the 2014 murders but guilty of the lesser charge of manslaughter due to "diminished responsibility", citing his heavy drug and alcohol abuse and sexual disorders.

The mutilated body of Sumarti Ningsih, 23, was found in a suitcase on the balcony of Jutting's apartment and Seneng Mujiasih, 26, was found inside the apartment with wounds to her neck and buttocks.

Prosecutor John Reading called Kavin Chow, an associate consultant at the Department of Forensic Psychiatry at Hong Kong's Castle Peak Hospital, to state that Jutting had moments of sobriety in between the killings and should have been able to resist "the use of substance".

Chow noted that Jutting acted rationally, ordering food for Ningsih before he killed her as well as cleaning up the bathroom afterwards.

"Despite the presence of abnormality of the mind it doesn't substantially impair his mental responsibility," she said.

Reading said Jutting called his mother after he killed Mujiasih, before he reported himself to police. Details of the conversation was not made clear in court.

The defense has called British experts in forensic psychiatry and psychology who have testified that Jutting has recognized disorders from cocaine and alcohol abuse as well as other personality disorders of sexual sadism and narcissism, which impaired his ability to control his behavior.

The defense has also argued that Jutting, a 31-year-old Cambridge university graduate, felt huge stress during his banking career.

Reading said Jutting only worked for 10-15 days in the month before he was arrested and only for a few hours a day. Jutting stopped responding queries form his work in the second week of October, 2014, just before the killings, said Reading.

Jutting, a former vice president and head of Structured Equity Finance & Trading (Asia) at Bank of America in Hong Kong, had felt great pressure when his boss told him his professional activities would be monitored, his defense has said.

The court heard on Tuesday that Jutting called his boss at the Bank of America after the killings, before he called the police, and warned him that the bank's reputation was at risk, defense lawyer Tim Owen said.

The trial, which is in its second week, has attracted international scrutiny due to Jutting's profile and the brutality of the killings in a city where crime is relatively low.

'NOT IMPULSIVE'

Jutting took hours of video on his iPhone as he tortured Ningsih. He also filmed monologues he called the "narcissistic ramblings of Rurik Jutting" in which he spoke of the murders, binged on cocaine and explained his violent sexual fantasies.

Freshly shaven and wearing a pale blue shirt, Jutting focused on the session intently on Wednesday, making notes as he sat in a sectioned off area, flanked by three policemen.

He smiled at times as his defense team challenged Chow, the prosecution witness.

Murder carries a mandatory life sentence, while manslaughter carries a maximum of life though a shorter sentence can be set.

Chow said Jutting had traits of a psychopathic and narcissistic personality but not a disorder.

Reading, referring to Chow's report, said Jutting had no close friends and would not share his feelings with others, only speaking to his younger brother. He was typified as coldly callous, promiscuous and superficially charming.

Reading detailed Jutting's openness to homosexuality. He quoted Jutting as saying he was "96 percent heterosexual" after having a few experiences with other males including have mutual oral sex aged 16 with a friend and full penetration with another male at Cambridge.

He enjoyed having rough sex and experimenting with a variety of sex workers, including having anal sex and urinating on them, Reading said.

Dr Oliver Chan, a medical officer at the Department of Forensic Psychiatry, at Castle Peak Hospital, said he believed it would be hard for Jutting to resist cocaine but it would "not deprive him of his ability to control himself".

Jutting's series of actions before and after the killings, including buying sex toys and hardware tools, "speaks against the notion he was out of control ... all I can say is it was not an impulsive act", Chan said.

(Reporting by Farah Master; Editing by Greg Torode, Robert Birsel)