It's never easy convincing someone to be in your documentary. Even if shooting goes well, you'll probably be bugging them for months afterward. You'll want to hang around their house. You'll want to talk to their family, their friends. And at the end of the process, if you're a filmmaker with integrity, they won't have any control over how they're depicted.

So you can understand why the subjects of The Secret Trial 5 might have been especially twitchy when Amar Wala said he wanted to interview them about what it was like to be held for years in a Canadian jail without charges.

"Obviously, some of them have trust issues," Wala says over the phone this week. "When you've been through what these subjects have been through, when you've lost what they've lost, including years of their lives, one of the few things you have left is your story. So it's very hard to trust someone with that."

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What they've been through is astonishing, especially if you believe that Canada regards civil liberties as sacred.

In 1999, Mahmoud Jaballah, a Scarborough high school principal, was arrested and detained without charge by the federal government, through the use of a murky mechanism in Canadian immigration law known as a security certificate. Over the following four years, another four men – Toronto's Mohammad Zeki Mahjoub, Hassan Almrei of Mississauga, Mohamed Harkat of Ottawa, and Adil Charkaoui of Montreal – were arrested and held without charge. (Spoiler alert: They're Muslim.)

Each spent between 21 months and more than seven years in prison, and years more under house arrest. Mahjoub is still living under house arrest. (Among the men, he alone declined to participate in the Secret Trial 5.)

Why has it taken the men so long to fight their incarceration? While the authorities freely leaked allegations to the press of terrorist-related activities – a front-page story in the Toronto Star wondered of Jaballah, "Is he a teacher or a terrorist?" – the actual evidence used in a security-certificate procedure is kept secret. (In keeping with the covert nature of the case, six government departments declined the filmmakers' requests for interviews: the Canadian Security Intelligence Service, Canada Border Services Agency, Public Safety Canada, Immigration Canada, Correctional Services Canada, and the Department of Justice.)

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If that seems unconstitutional, you're right: In February, 2007, the Supreme Court of Canada unanimously struck down the security-certificate system. But the government passed a modification to the law, which enabled the system to continue. The men challenged the new law last October; the Supreme Court is expected to rule on it some time this spring.

Wala began working on the film in 2009, shortly after graduating from the film production program at York University. He admits that he had no idea what he was getting into. "If you were to tell any 26-year-old that's trying to start making their first film, that he'd be 31 when it was done, and it would be extremely underfunded the entire time, and a very, very difficult struggle …" he trails off a little, then says: "This was a difficult few years."

"Now that it's getting a little bit of publicity and it's going to be seen at Hot Docs – which is a huge moment for us – it's definitely worth it. But looking back, there were definitely moments where I seriously considered quitting."

Secret Trial 5 is unusual among this year's collection of Canadian features at Hot Docs: While there are plenty of quietly political films, Wala's is the only one to directly challenge the federal government on one of the hottest issues of the day. "I think the general sense is that it's difficult to make a political film like this in Canada, particularly if you're going through the broadcast model," says Wala, referring to the common practice of securing a broadcast outlet – and funding from said broadcaster – before finishing the film.

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In the end, money came through from the Doc Ignite crowd-funding program at Hot Docs, as well as the Toronto Arts Council and Telefilm Canada.

"I think our film is a testament to why arts funding is so important in Canada," says Wala. "We've got government sources giving us funds for a film that is directly critical of the Canadian government. I think that's a really healthy practice for Canada."

The Secret Trial 5 will have its world premiere at Hot Docs on Saturday. For more information: hotdocs.ca.