Yang Zhao, 30, on Wednesday took the stand in his own defence after pleading not guilty to the murder of Qiong Yan, 29, in September 2020 at their inner-Brisbane apartment.
He has instead pleaded guilty to interfering with Ms Yan's corpse, which was found concealed in a large tool box on their unit's balcony about 10 months after her alleged murder.
Under cross examination by crown prosecutor Chris Cook, Zhao agreed he was a "coward" who told lies to police while they were looking for Ms Yan as a missing person.
"You admit you led the police on a wild goose chase?" Mr Cook said.
"Yes," Zhao, a Chinese national living in Australia on a student visa, said with the aid of a Mandarin interpreter.
Zhao said he lied to police again when he claimed he killed Ms Yan, as he wanted punishment for concealing her body and then stealing her money.
The Supreme Court jury previously heard Ms Yan's body was badly decomposed and damage to her forehead and neck were not conclusive evidence she was assaulted.
Under questioning from defence barrister Andrew Hoare, Zhao said Ms Yan's death was an accident while she was inhaling nitrous oxide, which he referred to as "laughing gas".
"Every evening we would do the gassing," Zhao said.
Zhao told the jury he had lied to a Queensland detective who phoned him on July 19, 2021 to ask about Ms Yan's whereabouts.
"You were scared of getting caught?" Mr Cook said.
"Yes," Zhao said.
The jury previously saw two police interview videos of Zhao telling detectives he killed Ms Yan by beating her on the head with a metal bottle then strangling her.
"I said those things because I wanted the death penalty to be imposed on me," Zhao said.
Zhao admitted he used Ms Yan's phone after her death and impersonated her in text messages to her mother to obtain up to $400,000 via bank transfers.
"I felt shamed by my actions," Zhao said.
Ms Yan was also a Chinese national and the director of a migration agency.
The jury heard Zhao and Ms Yan inhaled nitrous oxide between 9pm and 11pm at the apartment while Zhao also drank whiskey.
Ms Yan's mother Rongmei was in court to hear Zhao's evidence after travelling from Shanghai to Brisbane.
Zhao said Ms Yan had passed out on the apartment's floor after 11pm and he had fallen asleep on a sofa because he was "pretty high".
The jury heard Zhao woke up and took his dog for a 10-minute walk before returning at 1am.
"When I got closer I could see her body wasn't moving and she wasn't breathing," he said.
The jury heard Zhao always bought the nitrous oxide for himself and Ms Yan, buying nearly 200 small gas bulbs at a time.
"I was panicked. I was worried that I would get in trouble," Zhao said.
Zhao wiped away tears as he told the jury he wanted to end his own life after discovering Ms Yan had died.
He denied Mr Cook's claims that he was lying about feeling ashamed and wanting the death penalty.
He agreed he profited from Ms Yan's death but denied he murdered her and made up the account of her dying from nitrous oxide.
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