Errol Morris’s third documentary feature (after Gates of Heaven and Vernon, Florida) is an absorbing but problematic 1988 reconstruction of and investigation into the 1976 murder of a Dallas policeman. As an investigative detective-journalist who spent many years on this case, Morris uncovered a disturbing miscarriage of justice in the conviction of Randall Adams—who came very close to being executed. Morris goes so far in his talking-head interview technique that he eventually goads David Harris, Adams’s companion the night of the murder, into something very close to a confession. But Morris’s highly selective approach also leaves a good many questions hanging. The issue of motive is virtually untouched, and the quasi-abstract re-creations of the crime, accompanied by what is probably the first effective film score ever composed by Philip Glass, give rise to a lot of metaphysical speculations that, provocative as they are, only obfuscate the issues. The results, while compelling, provide an object lesson in the dangers of being influenced by Werner Herzog; the larger considerations and film noir overtones detract too much from the facts of the case, and what emerges are two effective half-films, each partially at odds with the other.