Moments before he surrendered after killing a second victim in his Hong Kong apartment, British banker Rurik Jutting ingested up to 20 grams of cocaine and imagined police were behind the curtains, a court heard on Thursday.

In videoed police interviews shown on the fourth day of his trial for the murder of two Indonesian women, Jutting impassively described the paranoia he felt moments before calling police to come and get him.

Jutting has admitted killing Sumarti Ningsih, a 23-year-old single mother, and another Indonesian woman, Seneng Mujiasih, as he acted out violent fantasies.

But the former investment banker pleaded not guilty to murder on grounds of diminished responsibility, while pleading guilty to the lesser crime of manslaughter.

Collapsing bloodsoaked and exhausted on his balcony after struggling to cut the throat of 26-year-old Mujiasih, the Cambridge University graduate told how he then yelled and waved a knife at people on the sidewalk 31 floors below.

"When I decided to surrender, I dropped my knife," Jutting said, describing how he barricaded himself into his bedroom and called police. He also dropped and smashed a bottle of vodka.

"I saw the curtains moving and I thought they (the police) were there," he said.

"I took the amount of cocaine for one or two days in half an hour."

The video evidence showed Rutting telling police that he was consuming 10 packs of cocaine a day - each costing HK$1,000 ($128.95). In earlier evidence, he said he was getting through 10 grams per day, washed down with red wine and Red Bull energy drinks. He complained of insomnia.

After surrendering, Jutting gave police his phone as "evidence", which contained photographs as well as four hours of video footage chronicling his cocaine and alcohol fueled spiral into an abyss of sexual torture and killing.

Dressed in a light blue shirt, Jutting, 31, sometimes shut his eyes and tilted his head upwards as the interviews played before the jury of four women and five men.

FINDING A COKE DEALER

During the police interviews, Jutting said he had enticed both victims back to his apartment by offering to pay for sex.

He also described the drug dealer who sold him the cocaine.

"It is all provided by Marvin, he's a black man," Jutting told police. "I was introduced to him by a sex worker...on a daily basis he has been selling me cocaine."

Jutting said he primarily "snorted" the drug but also inserted it into his rectum. He removed his shirt to show self-inflicted scratch marks, which he said was an effect of cocaine.

A toxicologist, called as an expert witness by the prosecution on Wednesday, described the quantities of cocaine consumed by Jutting during a six-week binge as unbelievably high.

The jury was earlier shown footage that Jutting filmed himself during the sexual torture and killing of Ningsih over the course of three days, capturing his taunts and boasts as well as his remorse and moments of self-loathing.

In videos played earlier in the trial, Jutting had described how he had crammed Ningsih's mutilated body in a suitcase which police found on the balcony. She had been visiting Hong Kong on a tourist visa, while Mujiasih had been working there as a domestic helper.

The High Court trial is due to continue next Monday, when the defense is due to open its case.

Murder carries a mandatory life sentence in Hong Kong, while manslaughter carries a maximum sentence of life.