Montreal filmmaker Frederic Bohbot structured his documentary Once a Nazi as a mystery - so viewers could make up their own minds about former Concordia professor Adalbert Lallier and his controversial past.

The one-hour doc recounts Lallier's well-publicized revelation in 1997 that, while a member of the Waffen SS, he saw his commander shoot seven Jewish prisoners. The film follows Lallier as he copes with the fallout of his disclosure, including testifying as a key witness at a war crimes trial in Germany.

While Lallier's account was instrumental in convicting his former commander, Julius Viel, in 2001, some observers accused him of coming forward to avoid being targeted by Nazi hunters himself.

"I didn't want people to judge him too quickly. Who knows what any of us would have done in the same situation?" says Bohbot, founder of Bunbury Films, who co-directed and coproduced with Evan Beloff of Montreal's Ontic Media (Winter Wonderland: The Making of the Ice Hotel).

But the doc's future is also something of a mystery, says Bohbot, noting that major broadcasters have been reluctant to get involved.

"They didn't believe the film had any relevance today. They generally saw it as simply another Holocaust story," he says.

Once a Nazi will air on Canal D, Access Alberta and SCN in the new year, however, and CTV has kicked in a small amount of post-production money earmarked for more in-depth research into Lallier's past, particularly his early years in Canada. As a result, the film could change slightly, says Bohbot. "CTV may require an adjustment."

Bohbot, who is Jewish, was a student of Lallier's when he went public. "I like him and I respect what he did, although I know there's so much that he chose not to tell me. In many ways I'm not sure exactly what happened. That's why we chose to structure it as a mystery based on one incident, rather than his entire time in the Waffen SS."

The film was shown in Montreal in September to good reviews and will screen at the Rencontres internationales du documentaire de Montréal, which runs from Nov. 9-19.