Hong Kong engineer on trial for stabbing his girlfriend 30 times over sex tape fight claims mental illness-induced blackout

A young civil engineer murdered his girlfriend by stabbing her 30 times on a moving bus after she mentioned wanting to break up and demanded the return of their sex tapes, prosecutors told a Hong Kong court on Tuesday.

But defendant Ng Yan-kin, 26, has said he had no recollection of the knife attack on September 16, 2017, with the defence arguing that the killing of 20-year-old Annie Li Sin-heng did not constitute murder, but was instead an act of manslaughter committed during an episode of a mental disorder.

The High Court heard the pair had met online and started dating in July 2016, just over a year before Ng stabbed Li to death with a newly purchased knife on the upper deck of Citybus No 118 five minutes after it departed from the terminus in Siu Sai Wan.

Rescuers arrived to find Li unconscious in a pool of blood, with her head resting on her thigh. She was certified dead at Pamela Youde Nethersole Eastern Hospital about 30 minutes later, with the cause of death found to be multiple stab wounds.

A forensic pathologist who studied the 33 knife wounds on her body surmised that she had been stabbed “forcefully”, as seen from the associated fractures.

Investigators later found recordings of Li’s conversations with Ng, as well as videos and photos of their sexual activities on his phone.

At issue in the case on Tuesday was whether Ng was suffering at the time from major depression and paranoid personality disorder, as his psychiatrist had claimed. If so, the condition would substantially impair his mental responsibility for the killing, reducing the act to the lesser charge of manslaughter.

Both murder and manslaughter are punishable by life in prison, though such a sentence is mandatory in murder cases. Prosecutors, however, have rejected that plea.

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“This is a murder,” senior assistant director of public prosecutions Derek Lai Kim-wah said in opening his case against Ng to a jury of five women and two men.

The prosecutor said the pair had a “smooth and happy” relationship at the beginning, and soon started recording their sexual activities in videos and photos, with Ng given copies.

But problems developed as Li reportedly found Ng “a controlling type of boyfriend”, who would get jealous and worry about her meeting other boys and becoming unfaithful.

“He always wanted to monitor Annie’s movements,” Lai continued. “He always wanted to know where Annie was.”

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Such fears allegedly led to arguments about whether Li should attend orientation camps at Polytechnic University as she transferred from an associate to a bachelor’s programme.

By early September of 2017, according to Ng, Li wanted to break up.

The prosecutor said Ng was unhappy about the idea and thought of committing suicide.

Meanwhile, Li was said to have asked Ng to return the recordings of their sexual activities, stored on memory cards, and Ng allegedly threatened to publish the materials.

In a conversation partially recorded on the defendant’s mobile phone in the early hours of September 16, Li was heard saying that she had decided to join the orientation camp, with Ng accusing her of breaking her promise not to go.

Lai said the conversation showed “considerable distrust” between the pair, as it showed that Li suspected Ng of keeping copies of the memory cards he had returned, while Ng in turn suspected Li of not deleting records of his threat as they had previously agreed.

Ng went to visit Li after waking up in the afternoon on the same day, but said he had no memory of what happened afterwards.

“The last memory he had was getting off the taxi; the next time he regained his memory was waking up in hospital at the intensive care unit,” the prosecutor said of the defence’s case. “But fortunately we have CCTV cameras.”

Security footage tracked Ng entering a shopping centre near Li’s home to buy a steel chef’s knife for HK$59.90 from JHC.

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Lai said Ng then followed Li onto the Citybus coach, where they were seen chatting briefly before he suddenly took the knife from his backpack and started stabbing her, warning other passengers not to approach.

Ng was then said to have stabbed himself several times before smashing the bus window with a hammer and jumping out from the upper deck of the stationary vehicle, landing on the pavement below.

The defendant was admitted to the same hospital as Li, where he stayed for four weeks before he was transferred to Castle Peak Hospital, then Siu Lam Psychiatric Centre.

His trial continues before Madam Justice Audrey Campbell-Moffat.