Vic murder accused found unfit to be tried

Of the seven criteria a person charged with a crime must meet in order to be fit to stand trial in Victoria, accused killer Jake Royd Fairest only meets one.

After deliberating for 10 minutes on Friday, a Victorian Supreme Court jury found the Boronia man was unfit to stand trial for the death of Robert Wright.

Fairest was charged with murder along with Georgia Fields and Warwick Toohey last year after Mr Wright fell to his death from the balcony of a Ringwood flat.

The victim and all three accused are profoundly deaf.

Following a committal hearing, the three accused each entered a plea of not guilty by reason of mental impairment.

The Supreme Court on Friday heard Fairest underwent aggressive cancer treatment as a seven-year-old that left him with an intellectual impairment.

He can neither read nor write.

His defence barrister David Gibson said Fairest's intellectual disability places him in the bottom .03 per cent of the population.

"He is unable to follow the course of a trial or give me instructions to defend him," Mr Gibson said.

Fairest's matter was unusual in that both the prosecution and defence agreed, Mr Gibson said.

Prosecutor Karen Argiropoulos said two psychologists both assessed Fairest and reached the same conclusion: that he was not fit to be tried.

Psychologist James Ogloff gave evidence Fairest did not meet six out of seven criteria set to test his fitness to stand trial.

Professor Michael Daffern said Fairest failed five of the seven.

Fairest's disability affects his memory, executive function, expressive language, problem solving, abstract reasoning and planning ability, the court heard.

Professor Daffern said Fairest had only a superficial understanding of what it meant to enter a plea.

"He was of the opinion that he was not guilty and that he would plead not guilty."

"In my opinion he is not able to follow the course of a trial."