A judge has slammed lawyers acting for a boy accused of murder for filing misleading information with the courts after failing to check documents created using artificial intelligence.

"It is not acceptable for AI to be used unless the product of that use is independently and thoroughly verified," Justice James Elliott told the Supreme Court in Melbourne.

The documents related to a 16-year-old boy, who was today found not guilty by way of mental impairment over the murder a 41-year-old woman in Abbotsford in April 2023.

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Prosecution, defence and two psychiatrists all agreed the boy, who cannot be legally named, was mentally impaired during the killing because he was suffering schizophrenic delusions.

His lawyers, including senior barrister Rishi Nathwani KC and his junior Amelia Beech, did not properly check their submissions before they were filed to the court containing errors, the court was told.

This included references to non-existent case citations and inaccurate quotes from a parliamentary speech.

Justice Elliott said the documents were not signed by barristers or solicitors when they were filed and defence admitted it had used AI when the court could not locate the referenced material.

The submissions were sent to prosecutors, who also did not verify all the information was correct and then created their own submissions based on the defence documents.

Defence apologised to the judge for the error and re-filed documents with the court.

But Justice Elliott said "the misleading information caused by AI did not end there" and the revised documents referred to made-up laws.

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"Revised submissions were not reviewed by either side … and referred to legislation that did not exist, an act that was appealed that never occurred," the judge said.

Defence apologised again and eventually filed their documents without AI inaccuracies.

"The manner in which these events have unfolded is unsatisfactory," Justice Elliott said.

He said the ability of the court to rely on submissions was "fundamental to the administration of justice" and all litigants should adhere to the Supreme Court's guidelines on AI.

"Use of AI without careful oversight of counsel would seriously undermine this court's ability to deliver justice," he said.

The guidelines state use of AI must not "directly mislead another participant in the litigation process as to the nature of any work understand or the content produced by that program".

Nathwani offered his "genuine and sincere apologies" to the judge and said he was embarrassed by what had occurred.

Prosecutor Daniel Porceddu also apologised and admitted he did not read the defence's references and citations.

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He did not further verify the documents' contents because he agreed with the conclusion reached in the defence submissions, he said.

The boy, who sat in court as the issue was raised, has been directed to remain under supervision at a Youth Justice Centre following the mental impairment finding.

He was accused, on the basis of complicity, of agreeing to commit the murder with a co-accused in order to steal the woman's car, drive to the Grampians, blow up a bridge and build an anti-communist army to take over Australia.

The plan was never enacted and he was arrested after the killing near Ballarat.

He was found to be mentally impaired during the offending as his schizophrenia was untreated at the time and he followed "grandiose delusions" that he was a prophet of God.

Justice Elliott noted, unlike in NSW, there are no adolescent psychiatric units in Victoria that he could be taken to.

He said he would continue to receive anti-psychotic treatment for his schizophrenia in youth justice.

The boy will return to court for a supervision hearing on November 5.

Support is available by calling Lifeline on 13 11 14, beyondblue on 1300 22 4636 or Kids Helpline 1800 55 1800 for people aged five to 25.