“Do you have any idea how hard it is to hand over your conscience to somebody else?” asks Deborah Lipstadt (Rachel Weisz), eyes wide. That’s the fascinating idea behind Mick Jackson’s drama “Denial,” based on a real-life lawsuit argued in a London courtroom in 2000. Lipstadt, an American historian and professor (early in her career, she was a faculty member in the University of Washington’s Jewish Studies department), was sued for libel in 1996 by British author and Holocaust denier David Irving (Timothy Spall). Refusing to settle the case, Lipstadt went to court – and had to sit quietly while British lawyers (led by Richard Rampton, played by Tom Wilkinson) argued her case for her.

It’s one of those stories that perhaps makes a better book than a movie (Lipstadt has written about the experience in the memoir “History on Trial: My Day in Court with a Holocaust Denier”). The film never finds a distinctive visual language, and screenwriter David Hare struggles to simplify a complex case. The characters here are constantly explaining legal matters to each other, for the benefit of the audience.

But ultimately “Denial” works, thanks to its strong cast – particularly Spall, who gives Irving a slightly mad gleefulness, and Weisz, whose smart, tough Deborah chafes against the quiet acquiescence expected of her. And the haunting story at its core speaks loudly. We see devastating glimpses of Auschwitz – the piles of suitcases, glasses, shoes – that remind us powerfully that this case isn’t about one woman. “It’s not for themselves,” Deborah argues to her attorneys, trying to get them to agree to let Holocaust survivors testify. “They want to give voice to the ones who didn’t make it.”