A FORMER boxer who once represented Australia decided to plead guilty to his crime at the last minute after a key witness came forward, a court has heard.
Jamie Reginald Hall, 28, faced the Hobart Supreme Court for sentencing on Friday.
He pleaded guilty to one count of armed robbery.
The crime occurred in the Glenorchy Centro newsagency about 4.30pm on November 22 last year.
Hall, wearing a hoodie and sunglasses, jumped the glass counter with a large knife hidden up his sleeve.
The knife fell out, and Hall picked it up and used it to threaten three staff members.
He grabbed a bag from the floor containing the next day's float, about $310, and fled.
Justice Shan Tennent noted Hall's lengthy criminal history, long-term drug use and lack of remorse.
She said jail was the only option.
"Your actions using a knife caused fear in your victims, and quite simply nobody should have to experience what you did," Justice Tennent said.
Hall's armed robbery breached a suspended sentence imposed on April 5, 2012.
Justice Tennent activated the suspended term and jailed Hall for three months.
For Hall's new offending, she jailed him for an additional 15 months.
Hall will be eligible for parole when he has served half that time.
He was due for release from his current jail term on March 6.
Justice Tennent referred to Hall's forensic mental health report and asked why it was requested, because there was no suggestion of mental illness.
"Your profile indicated a level of manic, impulsive and disorganised behaviours and that your thought processes during such behaviours were likely to be accelerated and marked by inflated self-esteem or grandiosity," she said.
Hall has more than 30 convictions for stealing and 23 for burglary, and has been dealt with for breaching suspended sentences.