Vic accused complicit in murder: Crown

A man accused of murdering a 33-year-old woman says he couldn't have predicted the hammer attack inflicted on her by her boyfriend that likely led to her death.

Simone Quinlan died in August 2015 after her boyfriend allegedly hit, kicked and hit her on the head with a hammer

Wayne Marmo, 25, is on trial accused of murdering Ms Quinlan after the assault when he shot her in the head five times as he drove her body to a mineshaft at Kangaroo Flat, near Bendigo, dumping her and setting her on fire.

In his closing address in the Supreme Court of Victoria on Thursday, prosecutor Kevin Doyle told the jury Marmo "indicated his approval" to Neil during the ice-fuelled assault on Ms Quinlan.

Mr Doyle said Marmo had produced a gun and began filing off its barrel with a hacksaw during Neil's "ice-raging" assault.

He said Marmo also reversed his ute up to Neil's doors, where the latter placed Ms Quinlan's body, wrapped in a blanket, in the tray.

He said witnesses to the event claimed Marmo had said to Neil that Ms Quinlan "snitched before ... imagine what she'd do now" and that he had to "get rid of her".

However, Marmo's defence lawyer Scott Johns told the jury it was a "big stretch" to say his client had encouraged Neil in his actions.

Mr Johns argued that Neil's hammer attack was "sudden and unexpected" and not something Marmo or any of the others present could have predicted.

He said Marmo had arrived at Neil's house to exchange stolen chainsaws for the drug ice and Neil had not needed anyone else's encouragement or assistance to bash his girlfriend.

Mr Johns reminded the jury of Neil's violent history and evidence about his anger toward Ms Quinlan, including her taking out an intervention order against him and starting up a relationship with another man.

"Brendan Neil's unpredictable, look at his history. None of them could tell how it would end, surely," he said.

"He had the motive, flew into a rage, grabbed the hammer and did it."

Mr Johns also said Marmo's gun was a "red herring" as far as his complicity in the assault.

He said Marmo filing the gun barrel was nothing "sinister", given firearms were a normal part of that group's world.

The closing addresses are expected to finish on Friday.