The celebrity-hunting former senior constable pleaded not guilty to murdering his ex Jesse Baird, 26, and Luke Davies, 29, saying he acted in self-defence.
The Crown alleges the former police officer shot Mr Baird execution-style after developing an infatuation and obsession with the TV presenter and carrying out a 13-part plan to murder him.
Mr Davies was then allegedly shot through a bedroom door to erase a witness.
One of the officer's friends told the NSW Supreme Court on Thursday she messaged him on February 16, 2024 - three days before the alleged murders - about a photo he posted online.
"I'd seen on social media he was with Kourtney Kardashian and Travis Barker while they were in Sydney," Stacey Parker said.
"I always wondered how he got so close to them ... Kourtney and Travis were just walking along."
Ms Parker, a West Australian resident, messaged Lamarre-Condon to see if he could get her a similar up-close experience with her favourite country music artist when she came to see them in Sydney the following month.
"If you can get to Kourt Kardash (sic), surely you can get us to Lainey Wilson," she said to Lamarre-Condon.
Ms Parker said she first met a teenage Lamarre-Condon in Sydney in 2010 while waiting outside the studio for Seven's Sunrise program to try to get a photo with US rapper Pitbull.
They kept in touch and met when Ms Parker came to Sydney once or twice a year, she told the court.
Four days after Lamarre-Condon posted the selfie with Kardashian, Ms Parker received a call from the then-police officer. It was a day after Mr Baird and Mr Davies were allegedly murdered.
"He told me he'd stolen some police files from the commissioner to do with COVID and wanted me to get rid of a phone," Ms Parker told the 15-member jury.
"I had to be 30 or 40km from my house, turn the phone on then turn it off and then throw it into a body of water."
Ms Parker never received the phone despite Lamarre-Condon telling her he would send it by express post.
Lamarre-Condon said she had to turn on the phone long enough to "ping", then turn it off.
The jury previously heard Lamarre-Condon took Mr Baird's phone and used it to message the 26-year-old's housemates, implying Mr Baird was taking a road trip to Perth.
During the COVID-19 pandemic, Ms Parker - who attended many anti-vaccination protests - asked the senior constable how he could "push back against people fighting for their freedoms".
"He said it was the Devil's work," Ms Parker said.
After years of communicating on Facebook and Instagram, Lamarre-Condon suddenly asked on February 13 to move their chats to the encrypted app Signal.
Two days after asking her to dispose of the phone, Lamarre-Condon called Ms Parker again in a different mood, she told the court.
"There's two guys missing in Sydney, he used to know one of them and he was being set up," Ms Parker recalled the accused saying to her.
The following day, Ms Parker saw a news story mentioning Lamarre-Condon as a person of interest in the two men's deaths and a detail saying Mr Baird's phone had sent a message saying he was going to Perth.
"I became concerned," Ms Parker said.
On Friday, the jury will be taken to a view of Mr Baird's Paddington terrace, where the two men were killed, and shown areas of forensic interest by crime scene officer Bronwyn Lansley.
The trial continues.
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