Zack Mavin, now 26, appeared in Sydney Supreme Court on Friday where he pleaded not guilty to murder and armed robbery.

He will face an estimated one-week trial in April 2023 focusing on his mental health at the time of the stabbing and attempted robbery at Shortland in December, 2020.

The matter had been delayed in the local court while both parties enlisted psychiatrists to provide reports assessing the mental health of Mr Mavin.

And on Friday Justice Helen Wilson asked if there was a dispute about whether Mr Mavin had a mental health defence available.

"The Crown does not consent to the entry of a verdict of act proven but not criminally responsible," a prosecutor said. "It will be a question for the evidence at trial."

Mr Palmer, 54, was taking his daughter's dog for a walk about 8pm on December 12, 2020, when he became involved in an argument with an armed man outside the Metro service station in Sandgate Road and was stabbed once in the abdomen.

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