Navy spy Jeffrey Delisle has been handed a 20-year sentence in federal prison for betraying his country by selling military secrets to the Russians.

The lengthy sentence stunned the 41-year-old naval intelligence officer – but was hailed by security experts and the Crown prosecutor as a significant deterrent to others thinking of engaging in similar treachery.

In addition, military officials are considering stopping Sub-Lieutenant Delisle's pay and recovering his salary since his arrest last year. A review is also under way into whether he should be released from the Canadian Forces.

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In his decision on Friday, Nova Scotia's Chief Judge of the Provincial Court, Patrick Curran, referred to the disgraced officer as a traitor, dismissing his explanation that his wife's betrayal of their marriage was a reason for "his own betrayal of the country."

He said the officer "coldly and rationally" offered his services to the Russians, receiving 23 payments amounting to $71,817 over nearly five years, beginning in 2007.

It took about 40 minutes for Judge Curran to read his decision before a packed courtroom. SLt. Delisle's mother, daughter and sister were sitting in the front row. No one showed any emotion.

"You are going to have to make this right, sir, with a substantial period of time in custody, which is going to take a big chunk out of the rest of your life," Judge Curran said. "That's a sad thing to look on perhaps through a certain set of eyes, but a necessary one looked on through the eyes of the public of Canada."

SLt. Delisle will be in prison for 18 years and five months because he was given credit for time served since his arrest on Jan. 13, 2012. It will be about six years before he can apply for parole.

He was also fined nearly $112,000 – this includes the regular payments from his Russian handlers and additional funds for future work. He has to pay that within 20 years.

General Tom Lawson, Chief of Defence Staff, said in a a statement after the sentencing that the Canadian Armed Forces "have entered one of the final stages in the process of dealing with the odious behaviour of SLt. Jeffrey Delisle."

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Although military experts who testified at the Delisle sentencing hearing last week said the officer's actions caused "exceptionally grave" harm to the country, Gen. Lawson did not go that far. He said SLt. Delisle's activities "could have placed this country's security at a higher risk."

Gen. Lawson also assured Canadians the military is reviewing its security procedures.

SLt. Delisle's lawyer, Mike Taylor, meanwhile, said after the sentencing that his client was in "shock."

"It's a significant sentence that he received, one that, quite frankly, I don't think he was really expecting," Mr. Taylor said. The defence lawyer did not rule out an appeal, expressing disappointment that Judge Curran ignored his arguments that the Crown did not prove exactly what damage his client's actions caused the country.

No one knows precisely what the military officer sold to the Russians; there is no record.

But security expert Christian Leuprecht, a political science professor at Queen's University and the Royal Military College, said that according to the judge, that is not relevant.

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"It doesn't matter what damage you do. If you pass information, you are guilty and you will go away for 20 years," Dr. Leuprecht said of the sentence, adding that he cannot recall the last time a Canadian judge referred to someone as a "traitor."

"This is very harsh language," he said.

This was the first test of the new Security of Information Act that was passed after the Sept. 11, 2001, terrorist attacks. The decision establishes a precedent.