The cinema of Errol Morris could be defined as the cinema of patience. Whether the work is his breakthrough documentary Gates of Heaven, in which two pet-cemetery owners-one successful, the other less so-gradually reveal their true selves, or his riveting The Thin Blue Line, in which a hitchhiker accused of killing a Dallas policeman is eventually proved to be innocent, Morris painstakingly allows the truth to unfold before a viewer's eyes.

This patient and courteous approach is taken again in Mr. Death: The Rise and Fall of Fred A. Leuchter, Jr., Morris' latest and arguably his darkest work to date. Leuchter, the eponymous Mr. Death, is a Malden, Massachusetts engineer who considers himself something of a humanist, one who would make capital punishment a kinder, if not agreeable, experience for those sentenced to death.

Dubbed the 'Florence Nightingale of Death Row,' the voluble Leuchter spends the dark but sprightly first third of Morris' movie explaining his views on designing and repairing gas chambers, electric chairs, gallows and lethal-injection systems, with occasional digressions about execution mishaps that could have been avoided. A chain smoker who, by his own count, goes through six packs of cigarettes and 20 cups of coffee a day, Leuchter initially strikes one as a well-meaning, if somewhat driven, character, given to wry, formal language-he calls Death Row inmates strapped into the electric chair 'executees'-but harmless enough. But appearances can be deceiving.

Leuchter's Florence Nightingale image began to totter in 1988 when a neo-Nazi named Ernst Zündel recruited him to visit Auschwitz to conduct a forensic investigation of poison gas in World War II Nazi concentration camps. The author of such tracts as 'The Hitler We Loved and Why' and 'Did Six Million Really Die?', Zündel hoped to buttress his contention that the Holocaust never happened, setting a trap for Leuchter, who, perhaps out of hubris, fell for Zündel's bait.

Following the sprightly first third or so of Morris' documentary, the shift from Leuchter the concerned, if eccentric, capital-punishment provider to Leuchter the Holocaust doubter is a bit of a leap. Then there is Mrs. Leuchter, a former waitress, who first met Fred back home when 'he came in on the way to the gun club.' The newlyweds spent their honeymoon at Auschwitz, where Fred conducted forensic tests on the use of poison gas and illegally took brick and mortar samples for analysis, concluding later that the Holocaust was fiction.

Ultimately, Morris' film is less about Fred Leuchter than it is about the lure and comfort of self-delusion. While the subject matter of Morris' film is highly charged, the filmmaker deftly steers the viewer through its more disturbing sequences and even finds room for his patented irony. At one point, Leuchter's newfound allies compare him favorably with George Washington and Thomas Jefferson. But, we are told, Mrs. Leuchter, the ex-waitress-to her credit-packed her bags and left him.

--Ed Kelleher