Former Sydney police officer Beau Lamarre-Condon will argue he acted in self defence on the day he is accused of murdering Sydney couple Jesse Baird and Luke Davies.
Mr Lamarre-Condon, 31, has pleaded not guilty to two counts of murder and one of aggravated break and enter.
His defence counsel urged jurors against rushing to reach any final conclusion until they have heard all of the evidence in the case.
The Crown has used an opening address to outline what it says was obsessive conduct towards Mr Baird and alleged stalking in the months leading up to February 2024, when the couple was allegedly shot dead in Mr Baird's Paddington terrace in Sydney's east.
Jurors have been told Mr Baird and the defendant had previously been romantically involved in 2022 and parts of the following year, but Mr Baird twice broke things off, including in mid-November 2023, and requested no further contact.
The Crown's case is that the then-senior constable disguised himself as an Uber Eats delivery driver, including with a helmet, when he entered the Brown Street property, shot Mr Baird twice in the kitchen, and then shot Mr Davies who was in a bedroom calling Triple Zero (000).
On Tuesday, Mr Lamarre-Condon's defence counsel John Stratton SC used his opening address to tell jurors the accused's case was that he did not murder either Mr Baird or Mr Davies, whose deaths he described as "a tragedy".
Mr Stratton said there would be no dispute his client was "very upset" by the second break-up and thought Mr Baird "had not been honest with him".
It was not disputed Mr Lamarre-Condon did some "stupid things" including looking through Mr Baird's phone, deleting contacts and deleting text messages, jurors were told.
And he admitted entering the Brown Street home on February 19, 2024, Mr Stratton said.
"His reason was that he wanted to recover some of his belongings including some jewellery … without having to go through the embarrassment of having a further meeting with Jesse Baird when he turned up at the door," he told the jury.
"He disguised himself … because he in fact was expecting there would be no-one home.
"He wore a helmet so he could masquerade as a delivery person if anyone unexpectedly opened the door."
Mr Stratton said it was Mr Lamarre-Condon's case that he had the gun with him because he was a police officer whose training told him he could not leave it unattended in a car.
Once inside, Mr Lamarre-Condon was "surprised" by Mr Baird who "understandably did not recognise him because he was wearing a motorcycle helmet", Mr Stratton said.
Mr Stratton said the two men attempted and the gun went off twice, fatally wounding Mr Baird, before it was flung into another room.
He said Mr Lamarre-Condon picked up a mobile phone and started calling Triple Zero, before he encountered Mr Davies as he walked towards the front door, where there was another struggle and Mr Lamarre-Condon pushed the gun away from himself.
"In the struggle that followed, Mr Davies pulled the trigger and fatally shot himself," Mr Stratton said.
The Crown has outlined what it says were steps Mr Lamarre-Condon took to conceal the alleged murders, including cleaning the house and disposing of the pair's bodies by unsuccessfully attempting to sink them in a dam near Goulburn.
Mr Stratton said it would be submitted that the conduct after the events at Brown Street "were not the actions of a man who believed he was guilty of murder, but the actions of a man who panicked considerably, and knew the gravity of the situation he was in and how it might be perceived".
He urged jurors against rushing to reach any final conclusion until they have heard all of the evidence in the case.
The trial, before Justice Natalie Adams, continues.