Walker had no viable home-detention address and his criminal history of nearly 50 convictions — and several stints behind bars — counted strongly against him.
His most recent jail term was imposed for sexual violence against a young person but it was not enough to keep him out of trouble.
On March 3, 21-year-old Melveen Singh messaged a friend suggesting they meet that day.
The weather was good and he proposed a swim at Aramoana.
The victim agreed and allowed Singh to drive his Holden Commodore to the isolated coastal settlement.
When they got there, the men opted for a walk instead of a dip in the sea.
The victim, however, was unaware Singh was in cahoots with Walker and their ruse was swiftly revealed as the men returned to the vehicle.
Walker confronted them and asked the victim what personal items he had on him.
The man, who later told police the incident had left him "terrified", thought the defendant's hand, conspicuously jammed in his hoodie pocket, may have held a knife.
An "agitated" Walker demanded cash until Singh intervened, informing him the victim had the keys to the car.
Reluctantly, he handed them over and was surprised the defendant went straight to the correct vehicle despite there being other Holdens parked nearby.
"Walker appeared to have already known which vehicle was the victim's," a police summary said.
The pretence now over, Singh and Walker together tried to get the car open.
When the victim tried to intervene, he was pushed by Singh then backed off when Walker threatened violence.
Judge Smith said the man had suffered ongoing psychological effects as a result of the incident.
Meanwhile, counsel David More emphasised his own client's mental-health struggles.
He told the court Walker was struggling at the time because he felt unsupported by agencies that were supposed to be assisting him.
"He says he simply gave up and went back to his drinking," More said.
Walker, who had been diagnosed with PTSD and suffered a "particularly difficult childhood", was now engaged with a psychologist and had lined up support for when he returned to the community.
The judge said the defendant had repeatedly been given chances to rehabilitate but nothing had stuck.
"You're caught in a cycle of criminal activity. There doesn't seem a likelihood, without real intervention, that you'll be able to stop it. You want to stop it but you simply have a paucity of resources," she said.
Judge Smith declined an Otago Daily Times application to photograph Walker.
Singh will be sentenced in November.
