A man who covered himself in black paint and armed himself with knives and a homemade explosive was impaired by mental illness when he attempted to rob a service station and stabbed a beloved father to death, a court has ruled.

Supreme Court Justice Stephen Campbell on Tuesday entered two special verdicts, finding that Zack Mavin, 26, attempted to rob a 7-Eleven and fatally stabbed Robert Palmer during an altercation however was not criminally responsible because he was suffering from paranoid schizophrenia at the time.

Mr Mavin, 26, faced trial in the Newcastle Supreme Court earlier this year after pleading not guilty to murder and attempted robbery on mental health grounds.

It was not disputed that Mr Mavin had stabbed Mr Palmer, leading to his death, outside a Shortland service station in Newcastle in December 2020.

The issue at trial was whether Mr Mavin’s actions were impacted by his mental illness.

The court was told that before stabbing Mr Palmer, Mr Mavin entered a Sandgate Rd service station and demanded money and cigarettes.

At the time, he was armed with two knives and a hammer.

He was also carrying a homemade incendiary device, containing ammonium nitrate and caustic soda, which when mixed together would combust.

“He said he knew about these things from ‘science’ and that he had used them before,” Justice Campbell said.

After being refused by the attendant, Mr Mavin mixed the two chemicals together and threw the device at the customer display screen, causing a small “very localised fire” on the floor.

He then walked out and up the road where he stabbed Mr Palmer, who was out walking his daughter’s dog, outside another service station.

The court was told that CCTV footage showed Mr Mavin and Mr Palmer standing “toe to toe” exchanging words.

Justice Campbell described Mr Mavin’s actions as “strange” and said he could be seen “dancing a small jig”.

Mr Palmer, the court was told, was backing away before Mr Mavin strode up to him and they exchanged blows.

Mr Palmer landed a punch on Mr Mavin’s jaw and Justice Campbell said: “At this point he drew the knife for the second time and is seen slashing at Mr Palmer as the latter backed away.

“The accused then lunged, moving his arm in a stabbing motion toward Mr Palmer. Although not clearly depicted on the footage, obviously he succeeded in stabbing Mr Palmer.”

Mr Mavin stabbed Mr Palmer in the abdomen before he walked off and was arrested on his veranda 15 minutes later, during which he had to be tasered because he did not comply with demands to drop his weapons.

The Crown prosecution argued that while Mr Mavin was suffering from schizophrenia, it was not to the extent to which a legal defence of mental illness had been established.

Following his arrest, when told he was being denied bail because he had been charged with murder, Mr Mavin told officers: “Nah, it’s not murder, it’s manslaughter, he came at me. No remorse.”

The court was told that he covered his face, hands and legs in black paint in an attempt to hide his identity and cover-up non-existent tattoos.

Justice Campbell found that Mr Mavin’s attempts to disguise himself instead drew attention to himself and led to him being arrested a short time later.

“The events have become so exaggerated in his own mind that he believed, as a product of his illness, that it was necessary to defend himself against the attack of Mr Palmer,” Justice Campbell said in his judgment handed down on Tuesday morning.

Mr Mavin will be detained under the care of the Mental Health Tribunal until he can be deemed safe for release.