A man sat with his bedridden mother and allegedly confessed to killing her de facto partner as the body lay in the entrance hallway.
The woman last saw Neal Keith Wilkinson alive when she took a morning dose of medication about 9am on Tuesday.
She awoke to find Jeffrey David Lee in her bedroom and asked where her partner of 29 years was.
Lee, 45, is alleged to have responded: "He's dead. I killed him."
Lee allegedly told his mother he had punched Mr Wilkinson, 61, after losing his temper.
He then asked her to give him 15 minutes before calling the police and left the Wanniassa home, police will allege.
The woman allegedly told police when they arrived, "My son was here, he killed my husband and carer".
Mr Wilkinson had suffered head injuries.
Lee, 45, was arrested on Wednesday and wore a white forensic jumpsuit when he appeared before the ACT Magistrates Court on Thursday afternoon.
He entered no plea and made no application for bail during the short appearance.
The court heard his mental health had been assessed during his time in custody and he was marked as a prisoner at risk.
Magistrate Maria Doogan noted the concerns involved his recent drug use.
Lee will reappear before the court again in April.
Court documents said Lee abandoned his car and went to a friend's home for help on Tuesday night.
Lee is alleged to have told the friend: "I f----- up, I punched him, he was bleeding, I blacked out, he was stiff."
Police will allege Lee told the man he had used ice and injected again in his presence.
The pair are alleged to have discussed ways for Lee to leave Canberra, including buying a car with NSW number plates.
But the friend did not believe Lee about the killing until he read a newspaper report the following day about a suspicious death in Wanniassa.
Police arrested Lee while he was walking a dog in O'Connor about 2.50pm on Wednesday.
An hour earlier, officers found and seized Lee's car.
Police allegedly found fingerprints, blood and bloodstained clothing, on and in the vehicle.
The evidence was collected and sent for forensic testing.
Upon his arrest, Lee consented to police taking non-intimate forensic samples, including fingerprints, fingernail scrapings, and his clothing.
Court documents said police investigators noted bruising and abrasions to the knuckles on both his hands.
Lee allegedly declined to comment during a police interview on Wednesday evening, but broke down in tears when asked about his mother's welfare.
Crime scene investigators continued to sift through evidence and the house remained taped off on Thursday.
Forensic teams combed the Wanniassa house and surrounding areas for evidence and seized several items in the hours after the alleged murder.
The RSPCA was called in to collect a cat found at the crime scene.
They said the couple had lived in the home for more than 20 years and were rarely seen outside.
The woman remains under observation in hospital.
with Megan Gorrey