For 14 years, John Kiriakou worked as an analyst and case officer for the CIA, leading the team that captured senior al-Qaeda member Abu Zubaydah in Pakistan in 2002. Then, in a television interview in 2007, three years after he had resigned from the US intelligence agency, he became the first current or former member of it to publicly acknowledge that the CIA used torture, and that its use was official policy under the administration of President George W Bush.

In 2012, the Barack Obama administration filed espionage charges against him.

Those charges were eventually dropped in October of that year, but Kiriakou did plead guilty to violating the Intelligence Identities Protection Act by confirming the name of an officer involved in the then-secret CIA rendition programme that transferred CIA detainees to secret prison facilities around the world.

He was sentenced to 30 months in prison and released in 2015 after serving almost two years.

Kiriakou, who has written the soon-to-be-released book, Doing Time Like a Spy: How the CIA Taught Me to Survive and Thrive in Prison, talks to Al Jazeera about the US's use of torture and his time in prison.

You were a CIA officer charged with protecting the US and its interests from global threats. How did you end up being imprisoned by the US government?

I decided to blow the whistle on the CIA's torture programme, which I believed was immoral, unethical and illegal. I gave a nationally televised interview in December 2007 in which I said that the CIA was torturing its prisoners, that torture was official US government policy and that the policy had been personally approved by the president [George W Bush].

It seems that classified information is regularly leaked by government officials, so what was different about your case?

Classified information is leaked every single day in Washington. The White House, the Pentagon and the CIA leak constantly. But I was prosecuted because I made the CIA look bad. I was prosecuted because I aired the CIA's dirty laundry.

There appears to have been an avalanche of leaks from the current White House but we haven't seen any legal action over them. How is the administration of Donald Trump different from that of his predecessor Barack Obama?

President Obama was obsessed with leaks more than any other president in history except, maybe, Richard Nixon. The CIA knew they had a friend in Obama. In the past, the CIA would either ignore leaks or work behind the scenes to plug them. But they wanted to make an example of me because I called them criminals.

In this book, you say that torture does not work and describe it as "un-American". Can you elaborate on your views on the use of torture?

I believe that torture is morally, ethically and legally wrong. We have laws in this country that specifically ban the kind of torture techniques that the CIA used against al-Qaeda prisoners. We just pretended that they were legal. At the same time, the CIA actually killed prisoners in custody using these techniques. Where is the justice for those people? I have come to the personal conclusion that we are supposed to be a country of laws. We are supposed to be a country governed by a constitution. We must follow all the laws, not just the ones that fit our own personal ideologies.

The Republicans who were the Senate minority in 2014 claimed that torture worked and had led to actionable intelligence, particularly from captured al-Qaeda leaders Abu Zubaydah and Khalid Sheikh Mohammed. How do you respond to this?

This is, simply, a lie. Yes, Abu Zubaydah provided that information. But he provided it to FBI agent Ali Soufan before the CIA started torturing him. None of that information was collected through the use of torture. Also, CIA leaders feel that they must justify their support for torture. It is their legacy.

Can you tell us about some of your own experiences of using torture and how these shaped your views on it? Did your opinions change over time?

The only personal experience that I had was in training when we took turns waterboarding each other. It was most definitely torture and it has no place in US policy. My personal opinion on torture has not changed. I tried to draw a distinction in that first interview [the 2007 TV interview]. I said there were two questions: Was torture moral, ethical and legal? Did torture work? The CIA has said for years that it worked. That was a lie. It was never moral, ethical or legal.

Do you think the American public is supportive of the use of torture and do you think they are fully informed about the ways in which it has been used?

I think, frankly, that most Americans are not well-informed. They believe whatever the government tells them. As a result, a majority of Americans support torture. But almost no Americans understand what torture is.

Trump has said that he supports the use of torture as an interrogation method, while spy chief Mike Pompeo is open to the idea of bringing back waterboarding. How do you feel about this?

This is a sickening position. It's a terrible thing that people as important as Trump and Pompeo would publicly advocate committing a crime. The positive thing is that with the passage of the McCain-Feinstein Amendment, the techniques that the CIA used are clearly illegal. They won't happen again.

[Senators John McCain and Dianne Feinstein introduced a bipartisan amendment to the National Defense Authorization Act for Fiscal Year 2016. The amendment was designed to prohibit the use of torture and restricts interrogation techniques to those authorised in the Army Field Manual. It also required access for the International Committee of the Red Cross to detainees in US government custody, which is current US policy.]

Given that the Feinstein-McCain Act prohibits the use of torture, do you think the administration could potentially outsource torture to some of its allies as it has done in the past, particularly in the Middle East?

I would not be surprised if the White House ordered the CIA to send prisoners or terrorist suspects to third countries to undergo torture. As a policy, the CIA asks its foreign partners specifically to not torture suspects. But torture allegedly takes place with a wink and a nod. I would not be at all surprised if the Trump administration asks the CIA to do exactly that.

Can you tell us about some of the people you encountered in prison, what you learned from that experience and how it has helped shape you?

I met some truly good people in prison. Our government likes to put people into categories - Aryans, Italians, gang members, Muslims, etc. I made friends among all of them.

What did your time in prison teach you about the American prison system?

My experience led me to the conclusion that the American prison system is broken. It is racist and it is anti-poor. It must be torn down and rebuilt. The US is home to five percent of the world's population, but 25 percent of the world's prison population. We are over-criminalised, over-legislated and over-regulated. This only weakens us as a country.

One of the most interesting things you mention in your book is that many of the prisoners at Loretto Federal prison chose to convert to Judaism. Can you tell us more about that?

Yes. Jews get much better food than anybody else because it has to be kosher. The average meal for regular prisoners costs something like 95 cents. But the kosher meal costs something like $2.35. The food is better, it's cleaner, and there's more of it. Also, Jews are allowed to buy extra treats around the Jewish holy days, like chocolate, soups, and other foods. Nobody else is allowed to have these foods. I once asked a Muslim friend why he didn't get halal meals. He said there were none. I said, "We have pork two or three times a week. What do you eat?" He said he throws the pork away and eats whatever is left. The Muslims did not get the same kind of treatment as the Jews.

Did your CIA training help you while in prison and, if so, how?

That's the whole point of the book. The CIA taught me 20 life rules that I used in prison. These rules kept me safe and healthy and kept me at the top of the social heap.

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