Former cabinet minister Colin Thatcher took the stand Tuesday at his faint hope hearing in Moose Jaw, Sask., and told a jury how he's managed to stay alive in prison.

Thatcher was convicted of first-degree murder and sentenced to life in prison for killing his ex-wife, JoAnn Wilson, in 1983. The conviction carried a mandatory life sentence without the possibility of parole for 25 years.

Thatcher is hoping for early release after serving just 19 years of his sentence, insisting that he is innocent.

Testifying Tuesday for the first time since the 1984 murder trial, Thatcher spoke about the time he has spent at the Edmonton Institution -- a prison where threats were made on his life as soon as he arrived.

He described the prison as a violent place where new inmates had to quickly "learn the ropes'' to avoid trouble. Thatcher, the only son of former Saskatchewan premier Ross Thatcher, testified he witnessed murders and assaults there.

"It was quite an experience,'' Thatcher recalled. ``Very quickly your attitudes and actions changed. "You don't see anything, you don't hear anything and, in a place like Edmonton, you learned that pretty quickly.''

He passed the time by researching his various appeals and writing a book. As his appeals were turned down, he said he began to accept his situation, though he always maintained he was not guilty.

Globe and Mail reporter Christie Blatchford, watching the case as it develops, says the fact Thatcher insists he was wrongfully convicted may actually work against him.

"The fact that he protests his innocence precludes any meaningful discussion of the actual crime," Blatchford told CTV's Canada AM. "But it also will make it more difficult for the jurors to feel comfortable that he's a changed guy."

As it closed its case Monday, the Crown's last witness told the 12-member Court of Queen's Bench jury that Thatcher's is, indeed, a complicated case.

B.C. psychiatrist Dr. Shabeharm Lohrasbe testified that Thatcher has psychological tendencies that could have led to an explosive rage at the breakup of his marriage. But he also said that a diagnosis remains elusive.

Lohrasbe testified that he found Thatcher careful, restrained and "almost completely unemotional'' -- at peace with the notion that he had been wrongfully convicted.

Blatchford said such an assessment is not surprising.

"He's very guarded emotionally and part of that is normal in a fellow who's spent so long behind bars. But it makes him difficult to read and to have confidence in your judgment of him."

She added that is going to complicate the jury's decision making.

"He has been a model inmate. The difficulty is, that's not akin to being a model citizen and that's part of what the jury has to decide."

Even if he is granted a sentence reduction, the final decision to release Thatcher early still rests with the National Parole Board.

With a report from The Canadian Press