The police officer, 31, has pleaded not guilty to the murders of Jesse Baird and Luke Davies, suggesting the men died after two separate struggles in Mr Baird's house in February 2024.
As the NSW Supreme Court trial entered its second week on Monday, close friend Georgia Cook continued giving evidence about a dinner she had with Lamarre-Condon.
"If you did kill someone, what would you do with their bodies?" Ms Cook said he asked her in May 2023.
When Ms Cook said she didn't know, the officer allegedly replied: "I would take their stuff, put it in a dumpster and I would take their bodies to bushland where no one would ever find them."
One of the officer's barristers put it to Ms Cook in cross-examination that she only included those details in a police statement after she heard them in media reporting on his arrest.
"When someone says something that scary or shocking, it's not something that leaves your mind," she said.
The senior constable accepts he entered Mr Baird's Paddington house in February 2024 armed with his police pistol and heavily disguised.
But the defence case is he did not intend to kill his former partner and did not shoot the other man, Mr Davies.
Ms Cook on Friday testified the senior constable also used the May 2023 dinner to confess to breaking into Mr Baird's home and stealing a camera he had given him as a gift.
Lamarre-Condon had on more than one occasion surveilled the home, using his mother's car and wearing a black hoodie to avoid detection, Ms Cook told the jury.
The former friend of the 31-year-old said the conversation caused an irreparable breakdown in their relationship, especially because Lamarre-Condon allegedly blackmailed her to not reveal his disposal planning.
Ms Cook had earlier told the officer about a private matter.
"What I'm about to tell you ... if you tell anyone else, I will go and tell people what I know about you," Lamarre-Condon allegedly warned her before discussing disposing a body.
As well as contesting two murder charges, Lamarre-Condon denies breaking into Mr Baird's home in August 2023 while disguised.
Lamarre-Condon's barrister has conceded his client did some "stupid things" but disputes he exhibited threatening behaviours before the fatal incident in the Paddington terrace.
"He never planned to kill or ever cause any harm to anyone," John Stratton SC has told jurors.
"It was in self-defence."
The trial continues.
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