John Kiriakou is waiting for a phone call. When it comes, he'll pack – say goodbye to his wife and five children. And then he'll go to jail for the next two and a half years.

The sentence was already agreed even before he made his final appearance in court. It was part of a plea deal. He said he was guilty and in return the government would propose a 30 month jail term.

The judge at the trial in Virginia was not impressed. Leonie M Brinkema insisted the sentence was "way too light". John Kiriakou knows if he had gone to trial, he could be facing at least 30 years in prison. At 48, it could be a life sentence.

John Kiriakou worked for the Central Intelligence Agency (CIA) for nearly 15 years. He received numerous commendations. He served in Pakistan and Greece and Bahrain.

Yet in the US, he's best known as one of the first former or current CIA officers to acknowledge that so called enhanced interrogation techniques were being used against "terror suspects". In one interview in 2007, he detailed the use of 'waterboarding'; essentially restraining a suspect, turning him upside down and pouring water over his face to simulate drowning.

Initially it appeared he was backing the use of such methods as a way to gain valuable information, particularly in the troubling months after the September 2001 attacks on the US. But then he became a more vocal critic of the practice. He made it clear he had never participated in such interviews. Sitting in his rented him in Northern Virginia, feeding his infant son lunch, he told me:

"Ever since I first heard the CIA had begun torturing prisoners I had a problem with it. I had a moral problem, an ethical problem with it. It's not something we were ever trained in. It's not something we were ever asked to do before September 11, indeed before we started capturing prisoners in 2002. I didn't think it was necessary".

But his high public profile was enough to make him a magnet for journalists who looked for his insight and advice, particularly on the work of the CIA.

One journalist asked him if he knew a man, Deuce Martinez, who had worked as an interrogator. John Kiriakou had worked with him, but was sure he'd retired, had never worked under cover and had placed a lot of his past on a public website. He passed on his details.

And then is when he broke the law. He told me: "Did I commit that crime? Yes, I did. I didn't have any intent to commit a crime. I didn't have any intent to harm this individual".

'Political case'

John Kiriakou was guilty of violating the Intelligence Identities Protection Act, a law passed in 1982 aimed at protecting undercover agents. And this gave him another notable first; the first current or CIA officer to be convicted of passing classified information to a reporter.

John Kiriakou, a tall dark haired Greek American insists he was arrested because he blew the whistle on torture: "I am absolutely certain and have been from the beginning that my case is not about leaks, it's about torture. And there are still people at very senior levels inside the CIA who are still furious with me for confirming that they were torturing prisoners. I have no doubt that this is a political case".

Prosecutors say the disclosures were just 'the tip of the iceberg'. The claimed that searches of the former agent's emails revealed he had given journalists information about dozens of other CIA officers and they said he did it out of a sense of ego, to boost his media profile, to publicise a forthcoming book and to gain lucrative consulting work.

The court was told his actions endangered the officer he named, and he had provided a victim impact statement. In a snapshot of the bizarre nature of the case, that could not be released to the open court or the public because parts of it were considered secret.

The judge too remained unmoved by statements by Kiriakou's expensive lawyers. "This is not a case of a whistleblower," said Judge Brinkema, "This is a case of a man who betrayed a solemn trust."

The decorated agent though believes he's paying the price for embarrassing the US government.

"The only person who is going to prison for having anything to do with the torture regime is the guy who blew the whistle on the torture. The torturers aren't going to prison. The people who ordered or conceived of the torture aren't going to prison. The attorneys who justified the torture aren't going to prison. And certainly at the top levels of the Bush administration who approved of the torture in the first place aren't going to prison"...

John Kiriakou knows he'll miss some important events over the next 30 months, christenings, birthdays, graduations. And he'll miss his wife and children. He's likely to spend time in a low security prison. He's not looking forward to jail, but he doesn't fear the phone call that will come summoning him to begin his sentence.

"I'm adaptable. The CIA taught me to be adaptable and I've lived in a lot worse places."

Follow Alan Fisher on Twitter: @AlanFisher