HALIFAX -- A naval officer who sold military secrets to Russia received a 20-year prison sentence Friday in a case that exposed Canadian security weaknesses and raised questions about the country's place in the intelligence community.

Sub-Lt. Jeffrey Paul Delisle rose in Nova Scotia provincial court as Judge Patrick Curran finished reading the 40-minute landmark decision, the first of its kind under the Security of Information Act.

His family members, including his mother, daughter and brother, sat quietly on the bench behind him as Curran ruled the officer will serve 18 years and five months behind bars because of time he has already served.

Curran dismissed Delisle's claim that his betrayal was triggered by heartbreak after learning his wife had cheated on him, saying the 41-year-old father of four "coldly and rationally authorized his services to Russia."

"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," Curran told the packed courtroom in Halifax.

"That's a sad thing looked on perhaps through a certain set of eyes, but a necessary one looked on through the eyes of the public of Canada."

Curran also ordered Delisle to pay a fine of $111,817-- the amount of money he collected from his Russian bosses over 4 1/2 years. He was given 20 years to pay it or face two more years in prison.

Defence lawyer Mike Taylor, who was asking for a sentence of no more than 10 years, said his client was stunned by the decision.

"He's still a little bit in shock," Taylor said. "It's a significant sentence that he received and one that, quite frankly, I don't think he was really expecting."

He said it was too early to determine whether he would appeal the decision.

Crown attorney Lyne Decarie said she was satisfied with Curran's ruling, stressing that deterrence was the focus of her case against the threat assessment analyst who had access to several top secret databases.

"I think he took into account the seriousness of this case," Decarie said outside court.

"Deterrence, deterrence, deterrence is of the utmost importance in these cases. ... This is not your usual, your typical type of criminality that you see every day."

The chief of defence staff issued a statement saying an administrative review will soon be finalized to determine how Delisle will be disciplined.

"Today, the Canadian Armed Forces have entered one of the final stages in the process dealing with the odious behaviour of Sub-Lt. Jeffrey Delisle," Gen. Tom Lawson said.

"Sub-Lt. Delisle failed each and every Canadian. With that said, I want to assure Canadians that we are actively pursuing measures to improve and enhance all facets of our security procedures."

But Lawson didn't specify what measures have been taken to plug leaks and beef up security screening.

Delisle pleaded guilty last October to breach of trust and communicating information that could harm Canada's interests to a foreign entity.

Reg Whitaker, an intelligence expert, said the ruling should please Canada's allies who were seeking a stiff penalty in a case that highlighted a series of embarrassing security lapses that allowed Delisle's deception to go undetected for years.

"I think anything less than that would have been seen as lax," Whitaker said from Victoria.

"The (U.S.) administration and senior ranks of agencies like the CIA and the FBI probably figure that it was a very big embarrassment for Canada and they're going to have to do an awful lot of work to try to get back into the position they used to have."

Rob Currie, a criminal law expert at Dalhousie University in Halifax, said the decision constituted a "big win" for the Crown and would send a message that this kind of behaviour would not be treated lightly.

"This is, by any measure, a stiff sentence under our law," he said. "Judge Curran emphasized the seriousness of the offence and the betrayal of the trust of the people of Canada."

In an agreed statement of facts, Delisle admitted that his treachery began in July 2007 when he walked into the Russian Embassy in Ottawa and offered his services for money.

From then on, he sought out classified information with the key word "Russia" and funnelled it to foreign agents for monthly payments of about $3,000.

In an expansive confession to the RCMP after his arrest in January 2012, Delisle revealed how he used floppy discs and memory sticks to smuggle data out of Halifax's HMCS Trinity, the military all-source intelligence centre on the East Coast.

He took the information home and copied it into an email address he shared with his Russian agent so he never had to send the email.

But he came under suspicion after returning in September 2011 from a trip to Brazil, where he met a Russian agent named Victor who told him that he would become a "pigeon" or liaison for all Russian agents in Canada.

Still, it took a tip from the FBI -- who noticed suspicious financial transactions -- for the RCMP to look into Delisle's activities. He was arrested after authorities intercepted two messages he tried to pass on to the Russians.

The Canadian Security Intelligence Service has said that Delisle's crimes could mean it receives less intelligence from allies in the future and it is still assessing the fallout of his actions.

The Crown argued that Delisle damaged Canada's relations with its allies, endangered intelligence agents and exposed their methods of gathering top-secret material.

But Taylor argued that the harm was "theoretical" since it isn't known exactly what secrets he leaked.

Curran downplayed that argument.

"I am satisfied that a person who discloses state secrets which have the potential to case substantial harm to the country's interests commits a grave offence whether or not actual harm has resulted," he said.