The man who tried to rob a Shortland service station while armed with knives, a hammer and an improvised bomb was likely impaired by mental illness at the time of the hold-up, a psychiatric expert has opined.
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But senior forensic psychiatrist Dr Stephen Allnutt could not say whether that was the case when Zack Mavin fatally stabbed Robert 'Bobby' Palmer soon after the failed heist.
Mr Mavin is facing a trial this week in Newcastle Supreme Court, after he pleaded not guilty to murder as well as a charge of attempted armed robbery at 7/11 on Sandgate Road on the night of December 12, 2020.
It is not in dispute that he tried to rob the service station or that he stabbed Mr Palmer in the abdomen during an altercation. The 61-year-old died at the scene.
Mr Mavin is raising a defence of mental health or cognitive impairment.
Dr Allnutt told the court on Tuesday it was his opinion that Mr Mavin had been moderately impaired by schizophrenia or a schizoaffective disorder at the time of the attempted armed robbery.
"I think that at this stage, on balance, if I was asked to fall on a side [regarding the attempted hold-up] ... I would say that he was impaired to a moderate degree," he said.
"Ultimately it's a legal decision and it's up to the adjudicator and there are still factors on both sides."
But Dr Allnutt said the impulsive nature of the stabbing made it difficult to determine whether mental illness had impacted the now 26-year-old's perception of what was morally right and wrong at the time.
"Impulsivity, by definition, doesn't take into account considering things," he said.
"That's the problem with an impulsive action - the person acts without thought."
In questions put to Dr Allnutt, defence barrister Paul Rosser, KC, argued his client's behaviour on the night in question was not rational.
The court heard Mr Mavin had painted his face and hands to cover tattoos he did not have, he stood in line and stepped aside when the attendant asked him to do so at the scene of the hold-up, he continued looking for cigarette butts on the ground between the attempted robbery and stabbing, and walked home after fatally injuring Mr Palmer.
The court also heard that Mr Mavin told police in the hours after the stabbing that Mr Palmer had "started it" and expressed surprise when he was informed he would not be released from custody that night - even after learning Mr Palmer had died. Mr Mavin told police he did not believe the stabbing was murder but that "at best it's manslaughter".
The court heard that Mr Mavin told Dr Allnutt a hallucinatory voice had instructed him to make the bomb used in the failed robbery.
Crown prosecutor Carl Young said Mr Mavin did not make any reference to a voice or other similar experiences during his interview with police on the night of the stabbing.
But Mr Rosser said police did not ask questions that would have prompted Mr Mavin to share that information with them.
The trial continues.
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