Errol Morris’s third documentary feature (after Gates of Heaven and Vernon, Florida), his most fascinating to date, is an absorbing but problematic 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 has uncovered a disturbing miscarriage of justice in the conviction of Randall Adams–who came very close to being executed, is currently serving a life sentence, and was most likely innocent–and the freeing of David Harris, who committed several violent crimes before and after this one (unlike Adams, who had a spotless record), and who was most likely guilty. Morris goes so far in his talking-head interview technique that he eventually goads Harris into something very close to a confession, but that technique also necessitates a highly selective treatment of the case that leaves a good many questions hanging. The issue of motive is virtually untouched by the film; and Morris’s quasi-abstract re-creations of the crime, accompanied by what is probably the first effective film score ever composed by Philip Glass, create a lot of metaphysical speculations that are provocative in themselves but further obfuscate many of the issues. The results are compelling, but a good 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. (Music Box, Friday through Thursday, September 16 through 22)