The man charged with the murder of police officer Jason Doig in South Australia’s south-east could mount a mental health defence but will admit to the “objective elements” of the case, his lawyer says.

The lawyer for Jaydn Harley Stimson asked the Adelaide Magistrates Court on Thursday to formally remand his client in mental health facility James Nash House.

Andrew Graham said Mr Stimson, 26, of Senior near the SA-Victoria border, has been housed at the facility since January without court order and it was “now appropriate that order be made”.

“There has been a diagnosis of a psychotic mental illness. In my submission it’s appropriate that it be noted,” he said.

“The objective elements of the offence will be admitted.”

Defence lawyer Andrew Graham said investigations are underway into Jaydn Stimson’s mental competence.(ABC News: Ben Pettitt)

He asked that his client be remanded under section 269 of the Criminal Law Consolidation Act, which provides guidelines for an accused who may have a mental impairment defence.

Mr Stimson is accused of shooting Brevet Sergeant Doig, 55, at his rural property north of Bordertown in November last year.

He is also charged with the attempted murder of Sergeant Michael Hutchinson.

Brevet Sergeant Jason Doig died while on duty near Bordertown on November 16.(Supplied: Facebook)

The court has previously heard Mr Stimson was shot by police during the incident.

Outside court, Mr Graham said his client did not have a diagnosed mental illness at the time of the incident in November, but that reports were being compiled for a formal diagnosis.

“He’s been diagnosed with a psychotic illness which is likely to be schizophrenia and what’s happening is we’re investigating his mental competence to commit the offences,” he said.

“We’ve received the brief from prosecution and the psychiatrist will be examining that and we’ll go from there.

“Just because someone has a psychotic illness doesn’t necessarily mean they’ve got a mental competence defence and that’s what we need to investigate.

“I don’t want to go too far into the evidence, but I don’t expect it’s going to be controversial that he was delusional at the time.”

Flowers outside Bordertown Police Station following the fatal shooting. (ABC News: Trent Murphy)

Mr Graham said he was unable to comment on the attempted murder charge.

Prosecutor Andrew Wilson told the court the murder and attempted murder charges would proceed as laid, and asked the matter be adjourned for 10 weeks.

Magistrate Brian Nitschke remanded Mr Stimson under the section — “the purpose of that being to have him detained at James Nash House”, he said.

The matter will return to court in June when Mr Stimson will be asked to enter a plea to each charge.