The couple had been arguing for months, with Ms Howell giving Charlton four weeks to leave her Hughesdale unit in Melbourne’s southeast.
Prosecutors allege he didn’t want to leave, instead killing Ms Howell on the night of April 21, 2007, after another one of their fights.
Charlton denies he murdered Ms Howell, telling police he returned home after walking the dog to find her bloodied and lifeless body at the bottom of the stairs.
He called emergency services about 11.20pm but she was later declared dead at the scene.
A post-mortem report found Ms Howell died from blunt force trauma to the back of the head and strangulation.
Prosecutor Patrick Bourke KC told a Victorian Supreme Court jury Charlton had the opportunity and the motive to murder Ms Howell.
“His relationship is doomed, it’s over,” Mr Bourke said on Tuesday.
“He’s been given his marching orders to leave but he won’t go.”
Charlton told police he had an argument with Ms Howell the evening she died where she called him an arsehole and threw a television remote into the backyard.
He said when he returned inside after collecting the remote, Ms Howell was upstairs in the bedroom so he took the dog for a walk.
Charlton maintains someone broke into the house through the garage and murdered Ms Howell while he was on his walk.
Mr Bourke told the jury there was no signs of struggle in the house, nothing was stolen and the garage door was intact.
Police also found a number of letters written by Ms Howell in the property, which said she didn’t want to continue with their relationship.
Ms Howell had repeatedly told her friends she wanted Charlton gone and she had given him a month to leave her home, Mr Bourke said.
Charlton’s barrister Megan Tittensor SC told the jury it was undisputed that Charlton and Ms Howell argued on the night she died.
But she argued police did not investigate other people who had the motive and opportunity to murder.
“He did not kill Ms Howell, he does not know who killed Ms Howell,” Ms Tittensor said.
The trial before Justice James Elliott will continue on Wednesday.
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