Fascinating historically, persuasive and probably correct theoretically, but flawed dramatically, this account of attorney Jim Garrison's pursuit of the Kennedy assassins raises the question why no-one has filmed it before - or been allowed to.

Far from the powerful document it might have been, the film still grips almost throughout because of the subject, and Garrison's examination and exploration of it.

Even director Oliver Stone's pretentious beginning and end-piece can't deny the enormity of the tragedy and its consequences.

Kevin Costner is not at his best as Garrison, seeming tired and lacking in conviction.

Sissy Spacek is poorly cast as his nagging wife, a part calling for a less sympathetic actress.

The only thoroughly believable performance comes from Jack Lemmon as a private eye reluctant to turn informant even for the little he knows.

No matter: the facts win out here. The deaths of many of those involved, including several key witnesses; the suppression or ignoring of evidence by others.

A horror film it is for sure - but there's not a monster in sight, at least not of the conventional kind.