Officer A, as he's known publicly for legal reasons, had pleaded not guilty to murdering Dwayne Johnstone outside Lismore Base Hospital on March 15, 2019.
After a three-week trial and nearly a week of deliberations, a NSW Supreme Court jury was discharged in November after failing to reach a verdict.
The case was mentioned on Thursday, when the prosecutor confirmed the officer will face a retrial.
Justice Robert Beech-Jones was told the earliest date suitable to both sides was October, due to the unavailability of witnesses and counsel at the same time before then.
He set the trial down for October 11 and listed the case for mention on April 20.
Mr Johnstone, 43, was being escorted out of the hospital when he shoved another prison officer and ran across the road, the first jury was told.
The Crown argued Mr Johnstone was posing no risk to anyone when shot.
Officer A drew his work-issued revolver, shouted a warning and then fired three times at Mr Johnstone whose wrists and ankles were restrained.
The last round struck Mr Johnstone in the back.
The officer's barrister submitted he was fulfilling a duty to prevent an escape, believing he and his colleague wouldn't be able to chase down the running prisoner.
Officer A yelled "stop or I'll shoot" twice and fired two warning shots, as per training for dealing with an escape, the barrister said.
Mr Johnstone had been arrested the day before and charged with assault and possession of a Taser.
He was taken to hospital after facing court and being remanded in custody.
12°C