Man 'stabbed mate while play fighting'

A man fatally stabbed his former housemate while play wrestling after he became upset about being put in a headlock, a Perth court has heard.

Dylan Anthony McColl is on trial in the West Australian Supreme Court accused of murdering 24-year-old Brent Charles Hurst Barton in Bunbury, in the state's south west, in May 2015.

The court heard on Tuesday that the pair previously had a falling out over money but remained friends.

In his opening address, prosecutor David Davidson said the pair were play fighting, as they often did, when McColl became aggressive after being put in a headlock.

Mr Barton allegedly told McColl: "Settle down man. It's only a joke ... I didn't mean to hurt you."

But McColl punched Mr Barton then waved a knife around before lunging at the victim's body, inflicting wounds that were 13cm and almost 16cm deep.

Mr Davidson told the jury there were witnesses to the murder.

But McColl's lawyer said his client denied stabbing the victim and alleged another man at the house was holding the knife.

The trial continues.