A driver accused of killing six people during a rampage through Melbourne’s Bourke Street believes God will exonerate him of guilt before a comet strikes Earth, the Supreme Court has been told.

James “Dimitrious” Gargasoulas on Monday faced day one of a hearing before a jury on Monday to determine if he is fit to stand trial on six counts of murder and 28 counts of attempted murder over the January 2017 incident.

Both the defence and prosecution agree Gargasoulas has schizophrenia and suffers delusions, but disagree whether he is fit to stand trial.

Defence barrister Theo Alexander argued Gargasoulas was unable to meet three criteria required of an accused person facing trial, including his ability to enter a plea, understand the substantial effect of evidence or instruct his lawyer.

But crown prosecutor Kerri Judd QC argued Gargasoulas was “not consumed by his delusional beliefs”.

She said he was making a bid to instead be held at Thomas Embling psychiatric hospital, with a possible future release.

The court was told Gargasoulas had treatment-resistant paranoid schizophrenia with “Messianic delusions”, and acknowledged he had ploughed through pedestrians last year but believed “God made him do it”.

Forensic psychiatrist Lester Walton told court Gargasoulas was on his sixth antipsychotic medication and was in the early stages of treatment with a “last resort”, potentially life-threatening drug.

Dr Walton said he believed Gargasoulas was unable to enter a plea due to his delusions, believing “he was acting under divine instruction” when he allegedly drove through pedestrians.

“‘My mission is to reinstate God’s law, which will redeem myself,'” he quoted from Gargasoulas.

“I will become king before the end of this court case.

“If I don’t reinstate God’s law, we are all going to die.”

Dr Walton said Gargasoulas could not “meaningfully enter a plea”, regarding that as “irrelevant” to his mission.

“He wants to be recognised as the king. This will happen, apparently, during the course of the trial once a comet arrives,” he said.

He added Gargasoulas believed that he needed to “have his day in court” to persuade everyone of his world view, “or we will all perish”.

Dr Walton, who spent about four hours assessing Gargasoulas in custody, said he didn’t believe he was mentally ill, but was a compliant patient.

Several experts are expected to testify during the fitness hearing, including forensic psychiatrist Andrew Carroll and forensic psychologist Michael Daffern, a prosecution witness, who will argue that Gargasoulas is in fact fit for trial.

The hearing continues.

-AAP