Ten pieces of evidence that show accused murderer knew stabbing was wrong: crown

Robert "Bobby" Palmer died after he was stabbed outside a service station at Shortland in December, 2020. Zack Mavin is facing a murder trial in NSW Supreme Court.

HE wore a disguise, "premeditated" robbing a service station, did not want to hurt anyone but took a large knife "in case s--- got bad" and stabbed well-known Shortland local Robert "Bobby" Palmer during a fight because the 61-year-old was bigger than him.

And, later, when he was told he was being charged with murder, Zack Mavin replied: "At best it is manslaughter, mate."

These are just some of the pieces of evidence that show that, despite suffering from schizophrenia, Mr Mavin knew what he was doing was wrong when he stabbed Mr Palmer to death outside a service station at Shortland in December, 2020, Newcastle Supreme Court has heard.

Mr Mavin does not deny the stabbing but has pleaded not guilty to murder and attempted armed robbery and raised a defence of mental health or cognitive impairment.

There is no dispute between psychiatric experts that Mr Mavin was suffering from schizophrenia at the time of the stabbing, but a judge-alone trial this week has focused on whether Mr Mavin, now 26, knew whether his actions were right or wrong.

During his closing address on Thursday, Crown prosecutor Carl Young outlined for Justice Stephen Campbell what he said were ten pieces of evidence that showed Mr Mavin knew the moral or legal wrongfulness of his actions on the night he attempted to rob one service station on Sandgate Road and then fatally stabbed Mr Palmer outside another.

He pointed to evidence that Mr Mavin had disguised himself before the robbery, which he told police he "premeditated", discussed a motive for the robbery and indicated he did not want to hurt anyone but brought the knife in case "s--- got bad".

And he said Mr Mavin's reaction to the service station operator fleeing out the back during the robbery might have been strange - he was annoyed the victim had cared only for his own safety and not for others in the shop - but it showed he did have some capacity to understand right and wrong.

Emergency services outside the Metro service station at Shortland after Robert Palmer was stabbed in 2020.

And he said the fact Mr Mavin had outlined motivations for the robbery and the stabbing and had said he then was "lying low" before the police arrested him showed he knew what he was doing was wrong.

Finally, he said Mr Mavin arguing with police that it was "manslaughter at best" and not murder showed he knew he had committed a crime.

"Your Honour may find some of those more persuasive than others but in combination they point powerfully to a thought process of not just legal wrongfulness but moral wrongfulness as to his actions on the night," Mr Young said.

Defence barrister, Paul Rosser, KC, used his closing address to pick apart Mr Young's submissions on the crucial evidence and said schizophrenia was an illness where "sensible thoughts are capable of existing together with rational thoughts", urging Justice Campbell to look at the overall picture.

Justice Campbell said it was a complex case and he would need some time to deliberate before delivering judgment next Friday.

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