Kings Park siege man unfit for sentencing

A mentally unwell man who held his elderly father hostage in Perth's Kings Park has had his sentencing postponed, with the judge saying the man is still ill.

In July 2012, David Charles Batty held his then 79-year-old father hostage in a car and threatened police with a gas bottle and a lighter in the CBD park, with the stand-off ending after police fired non-lethal beanbag rounds.

Batty fled psychiatric hospital Graylands in May 2014, two months after he pleaded guilty to three offences and before he could be sentenced.

On Tuesday in the West Australian District Court, Chief Judge Kevin Frederick Sleight said Batty, who was suffering from psychosis at the time of the siege, could not yet be sentenced.

Chief Judge Sleight said Batty's guilty plea was inconsistent with the latest psychiatric report, which stated he was not capable of understanding the implications of the sentencing process.

"It would be reckless of me to form a different view," the judge said.

The prosecutor said while Batty was insane at the time of the offences, he was mentally fit when he admitted them.

Chief Judge Sleight noted the difficulty faced by Batty's defence lawyer, because if he had pleaded not guilty and was acquitted on the basis of insanity, he would be detained indefinitely as an involuntary psychiatric patient.

"It is clear that he is a risk to the public," the prosecutor said.

"How long he will stay in the psychiatric system is difficult to answer."

Batty is being detained at the maximum-security Frankland Centre at Graylands.

Chief Judge Sleight instructed the lawyers to prepare supplementary written submissions, noting his two options were to consider setting aside the guilty pleas or proceeding with sentencing.

The matter was adjourned until March 1.