British banker 'needed cocaine boost' to torture and kill two women in Hong Kong

'Let's be clear about these, I am going to use these to torture someone in the most inhumane way possible,' Cambridge University graduate says in self-made video

Rurik Jutting, a British banker, sitting in a prison bus (AP)

Prosecution and defence lawyers used their closing arguments on Friday to try to convince a Hong Kong jury of the extent British banker Rurik Jutting was in control of his actions when he tortured, raped and killed two Indonesian women.

Jutting, 31, a former Bank of America Corp employee, has denied murder in the 2014 killings of Sumarti Ningsih, 23, and Seneng Mujiasih, 26, on the grounds of diminished responsibility. He has pleaded guilty to the lesser charge of manslaughter.

The judge is expected to sum up the case on Monday and a verdict is expected on Tuesday.

The prosecution told the court that Jutting needed the "boost" of cocaine to commit the crimes in his luxury high-rise apartment in a case that has received widespread international attention.

The prosecution has stated the former Cambridge University graduate was able to form judgements and exercise self-control, describing when he cut Ningsih's neck as she knelt by the toilet bowl and later dragged her to the shower to finish sawing her neck.

"He needed the boost of cocaine to give him the courage to rape, torture and ultimately kill," prosecution lawyer John Reading said, explaining that despite Jutting's disorders his "mental responsibility was not substantially impaired".

Reading detailed Jutting's plan to torture Mujiasih, his buying of items including a hammer and pliers from a hardware store, and his hiding of two knives.

"Let's be clear about these, I am going to use these to torture someone in the most inhumane way possible," Reading said, citing one of Jutting's self-made videos.

The prosecution said on Wednesday Jutting acted rationally before and after the killings and had even telephoned his mother.

Jutting captured parts of his torture of Ningsih on his iPhone. He also shot hours of himself discussing the killings, cocaine binges and detailed his violent sexual fantasies.

The footage has been shown to the jury during the two-week trial while the court has been packed with reporters due Jutting's profile and the nature of the killings in a city where such crime is rare.

Sitting in a sectioned-off area in the court, Jutting, who has an IQ in the top 1 percent of the population according to the defence, watched the arguments with a blank expression. He has attended the trial every day, escorted by three policemen.

Jutting, the grandson of a British policeman in Hong Kong and an ethnic Chinese woman, was a former vice president and head of Structured Equity Finance and Trading (Asia) at Bank of America. The bank declined to comment.

The defence has argued that Jutting's recognised disorders from cocaine and alcohol abuse on top of other personality disorders of sexual sadism and narcissism impaired his ability to control his behaviour.

Defence lawyer Tim Owen said Jutting was not "asking for sympathy" and acknowledged he intended to kill both victims. However, he argued that manslaughter and diminished responsibility applied because he was not able to make rational decisions.

"Not all killings are the same," Owen told the jury. "I am asking you to do no more than ask you how his actions should be defined in legal terms ... This is a court of law, it not a court of morals."

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

Owen detailed Jutting's stressful working life describing the start of a negative spiral after a complex tax product in Luxembourg Jutting worked on in 2012 which flagged him as "representing serious risk" to Bank of America.

He explained how Jutting was involved in a "battle of wills" with the auditor and was asked by his boss to "calm down, have a quiet year and was pushed to a different part of the business" before being sent to Hong Kong in 2013.

"That kind of setback of his brilliance, of his destiny, is something he couldn't handle and was the start of what became a very, very serious and rapid decline."

Jutting drank a bottle of spirits every day and consumed increasing amounts of cocaine after arriving in Hong Kong, the court heard. He only worked for 10 to 15 days in the month before he was arrested and only worked a few hours per day.

Police have testified that they found Ningsih and Mujiasih's bodies in Jutting's apartment after he called them to report the killings. Ningsih's mutilated body was found in a suitcase on the balcony, while Mujiasih's was found inside the apartment with wounds to her neck and buttocks.

Reuters