Donald Morley faced the ACT Supreme Court via audio-visual link on Friday.

Legal Aid lawyer Nathan Deakes, who appeared on video alongside his client, asked the court's permission for Morley to remain seated during proceedings "due to frailty at this time".

Morley could been seen sitting in a chair, bandages wrapped around the top of his head.

The 92-year-old was asked how he would plead to a charge of murdering his wife, Jean Morley, on July 30.

"Guilty," he responded.

The court heard there were no fitness to plead issues.

Morley is currently being held at North Canberra Hospital's older persons mental health unit.

Mrs Morley, who had dementia, was found in July at a Fisher home where the couple had lived for more than 45 years.

It is believed Morley is the oldest person to be charged with murder in the ACT.

According to police documents previously tendered to the court, Morley told a registered nurse who discovered Mrs Morley he had "done a terrible thing".

"I suffocated her with a pillow last night."

Morley allegedly said he had killed his wife about 9pm the night before.

He also told the nurse, who visited the resident twice weekly to tend to the man, he had tried to kill himself in multiple ways.

In what police believe to be a suicide note, Morley allegedly claimed that "after 69 years married, we were both afraid of the future".

"Please don't call this 'murder'-suicide," he allegedly said in the note.

"Sorry to upset all our family and friends this wasn't easy for me, especially my darling."

Morley has been in custody since his arrest on July 31.

The case is set to go before a registrar next week, when a date may be determined for a sentencing hearing.