A prisoner doing time over his role in a violent robbery in central Canberra has refused to give detailed evidence about the incident because his "arse is on the line" in jail.
The inmate, Aren Apps, pleaded guilty to an agreed statement of facts that didn't identify his co-offender.
On Monday, prosecutor Sarah McFarland alleged the co-offender was Michael John Mundy; a man who fronted the first day of a judge-alone trial in the ACT Supreme Court.
But the trial was abandoned only hours in. Mr Mundy pleaded not guilty to one count of robbery in company, and Apps did not identify him as his co-offender.
That lack of identification, as well as a "continuity" issue with an item police seized, meant prosecutors chose to withdraw the charge against Mr Mundy and not proceed with the trial.
Beforehand, Ms McFarland alleged Mr Mundy and the prisoner approached a stranger and asked him for a cigarette in the early hours of March 7, 2019.
She said when the stranger declined, he was "set upon" and stabbed multiple times with a screwdriver, including in the chest. The victim later told police, "I thought he was punching me at first, and then he came away and I noticed he had [the weapon]".
Ms McFarland alleged the pair took the victim to an ATM. The victim said one of the two men demanded, "Give me your PIN number or I'll stab you again".
He said he couldn't remember handing over his details but he must have, given his bank records showed $1900 had been taken out of his account.
CCTV footage showed the man falling to the ground outside the ATM as Apps stood behind him and another man grabbed the cash over three separate transactions.
Apps appeared in court via audio-visual link from the Alexander Maconochie Centre on Monday, and told the prosecutor he'd only met his co-offender on the night of the crime.
He said he was at a service station getting a slushie when they first spoke, and the robbery was a "spur of the moment" thing. "I'd been on the drugs for five, six days ... it was a bit how you going," he said.
The prisoner said he remembered asking the victim, who had a full pack of cigarettes, if he could have one. He said things "just broke out" when the man declined the request.
Ms McFarland put to the prisoner that Mr Mundy was a friend of his and they'd done the robbery together.
But Apps said he didn't know his co-offender's name, and wouldn't elaborate on the details of the incident further.
"You know how dangerous it is [here] when you go and give evidence on people," Apps said.
"If you're known as a dog in jail, you get bashed ... I'm not risking my life for anybody."
Lawyer Sam McLaughlin said it wasn't surprising Apps couldn't remember some of the details of the incident given he'd been on a "five-day bender".
He said Mr Mundy wasn't the prisoner's co-offender during the robbery.
After Apps gave evidence and the continuity issue was identified, prosecutors withdrew the charge against Mr Mundy and Chief Justice Helen Murrell abandoned the trial.