This movie is no ‘12 Angry Men,’ and Robert Redford is no Sidney Lumet.

Once upon a time—in the era of Sidney Lumet’s 12 Angry Men (1957), say—Robert Redford’s The Conspirator could have been the kind of movie that liberal high-school teachers expected their students to see. It’s good for you. For, in its narrative of the trial of Mary Surratt for complicity in the assassination of President Abraham Lincoln, The Conspirator is doggedly on the side of decent, fair trials conducted according to the Constitution, with discovery, proper cross-examination and objection, and a jury of your peers—instead of those nasty military tribunals where the government has scripted its verdict in advance and stacked the court with pliant officers so the process plays out tidily for the sake of “public order” and reassurance. Redford’s heart and his head are superimposed. This is seldom encouraging to intelligence or sentiment, and the film’s stalwart disapproval of our judicial excesses since September 11 leaves it only a fraction as compelling as the allegedly old-fashioned 12 Angry Men.

One of the problems with The Conspirator (as scripted by James Solomon and directed by Redford) is that we’re never quite sure to whom the title refers. It could be Mary Surratt herself, of course, the owner of a Washington boarding house and an out-of-town inn, both properties frequented by the conspirators against Lincoln, and the victim of a few pieces of circumstantial evidence. Surratt is played by Robin Wright—who can be attractive and subtle, but not here. She plays Surratt under an implacable and inscrutable death-mask. The actress is spared the menstrual cramps that kept the real Surratt out of court on some days, but she has been asked to be a victim primed for suffering, whereas Redford’s liberal indignation about her noxious trial would be justified even if she was guilty and interesting.

So, if “the conspirator” is not Mary Surratt, is it one of the trio of hissable male authorities who fix the case against her? Secretary of War Edwin M. Stanton (Kevin Kline), a willful leader in emergency, determined to execute the woman; Joseph Holt (Danny Huston), the silky cynic who is the prosecuting attorney; or General Hunter (Colm Meaney), the dogmatic, brutish president of the court who is clearly trying out for a Stalin show trial?

Or is it even the stubborn Frederick Aiken (James McAvoy), the brave Union captain now restored to the law and likely to lose his fiancé, his friends, and his career prospects as he warms to the task of defending Surratt? At first, Aiken does not want the awkward job that the calculating Senator Reverdy Johnson (Tom Wilkinson) has dropped on him (this Johnson is seen playing chess with himself as he takes a solitary dinner!), but then, McAvoy’s eyes widen, and you realize Redford has been talking to him and getting him to see the light about military tribunals. It’s worth adding this information from a post-movie title: that Aiken gave up on the law after losing this case and eventually became editor of The Washington Post—one or two degrees of separation from Ben Bradlee, All the President’s Men, and Bob Woodward (as played by Robert Redford).

If you think back on 12 Angry Men (a 95-minute film, where this one is 123), just marvel at how fully we came to know those jurors, eleven of whom were unexpected individuals—I exclude Henry Fonda in his white jacket because he is the teacher saint (and that jury had no women!). One of the jurors—Lee J. Cobb—was a “bad” guy, if you like, but the others were only weak, muddled, and plausibly human. In The Conspirator, actors as good as Kline, Meaney, and Huston are encouraged to make their characters hateful and one-sided. Yet a better film ought to have shown how genuine apprehension and an acute sense of politics prompted their actions. It might also have alluded to the way John Wilkes Booth himself was not just a heartfelt Confederate but a less than noble actor looking for melodrama