Bobby Palmer murder trial to focus on Zack Mavin 's mental health at time of Shortland stabbing

But the impact his schizophrenia had on his actions that night and whether Mr Mavin, now 26, knew what he was doing was wrong will be the focus of a judge-alone trial in Newcastle Supreme Court this week.

Mr Mavin, who is represented by barrister Paul Rosser, KC, and solicitor John Anthony, was on Monday arraigned and pleaded not guilty to murder and attempted armed robbery, raising a defence of mental health or cognitive impairment.

During his opening address, Crown prosecutor Carl Young said there was no dispute Mr Mavin had tried to hold up the 7/11 service station on Sandgate Road at Shortland about 8pm on December 12, 2020, and then, a few minutes later, had stabbed Mr Palmer during an argument and struggle outside the nearby Metro service station.

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Mr Palmer was stabbed once in the abdomen and died at the scene, his death triggering an outpouring of grief in the tight-knit community.

Mr Young also said there was no dispute between medical experts that Mr Mavin had a mental health impairment on the night of the stabbing and was suffering from schizophrenia.

"The primary issue in this trial is the impact that his schizophrenia had on his actions on the evening and in particular whether Your Honour can be satisfied on the balance of probabilities that at the time the accused did not know what he was doing was wrong," Mr Young told Justice Stephen Campbell.

Much of the events of the night, including the robbery and stabbing, were captured on CCTV and mobile phone footage, a compilation of that video played for Justice Campbell on Monday.

Heavily armed and with a black substance smeared on his body to disguise himself, Mr Mavin walked up and down Sandgate Road before walking into the 7/11 service station and demanding cash and cigarettes.

When the attendant asked for money, Mr Mavin replied: "I don't have any f---ing money.... just give me the f---ing smokes or I'll kill you with the chloroform bomb".

He then mixed the contents of two bottles, shook one of the bottles and threw it at the counter, but it bounced back towards him and later started a small fire.

Mr Mavin then left and walked towards the Metro service station, a few hundred metres away down Sandgate Road.

Meanwhile, Mr Palmer was taking his daughter's dog for a walk and was headed to the service station to buy coffee and cigarettes.

He was walking to the 7/11, but was told by someone about the armed robbery and turned around and started heading towards the Metro where he would ultimately come into contact with Mr Mavin, a stranger to him, and be stabbed to death.

CCTV footage from outside the service station captured the pair speaking for about a minute and witnesses later said they thought they were arguing.

Mr Mavin then slashed at Mr Palmer as he backed away, but the pair separated and Mr Mavin was walking away.

But something was said and Mr Mavin returned, walking aggressively towards Mr Palmer as he backed away. The pair came together and punched each other before Mr Mavin produced a large kitchen knife and again advanced aggressively, slashing at Mr Palmer, before stabbing him once.

Mr Mavin was arrested at a home nearby and had to be tasered and later capsicum sprayed by police.

During his brief opening address, Mr Rosser agreed the focus of the trial was narrowed to Mr Mavin's state of mind and much of the factual issues about what happened that night were not in dispute.

"The defence case is when one looks at the objective features of what the accused did and when one adds to that some very unusual statements in the course of his interview, you would ultimately be persuaded that the [mental health and cognitive impairment] issue should be decided in his favour," Mr Rosser said.

The trial will continue on Tuesday when the first of the psychiatric experts are expected to give evidence.

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