Mr Death (Dir. Errol Morris)

This nightmarish portrait begins in typical style. Morris's trademark long slow shots with music and voice over might not be revolutionary but it's classy and functional. I'm often baffled by 'rise and fall' documentaries, the logistics of maintaining subject access must be a minefield but it always pays off, we love to see a good fail.
Our subject Fred Leuchter is introduced as an electrical engineer that somehow found himself working within his own niche. Following claims of empathy for humans on death row, Fred made a career out of redesigning and refining all of 'the four' methods of execution. The plot thickens exponentially as Fred is recruited by a team of holocaust deniers as their 'scientist'. For reasons that escape me, they believe Fred's status as an execution expert gives him some credibility as a historian and forensic scientist. Get this, he actually takes his wife on a honeymoon... to Auschwitz. There, he clumsily collects samples of concrete from the walls of Auschwitz' gas chambers and concentration camps. Fred finds himself knee deep in this 'debate' and in fact falls in line with the Holocaust deniers producing evidence in defense of their claims. You can't help but get that sinking feeling as Fred asks, "Well, why didn't they just shoot them?...it just doesn't make much sense". Next thing he is releasing reports through the Aryan print propaganda magazine and 'dispelling the myth' of the holocaust at neo-nazi rallies. As holes are quickly poked in Fred's science one scientist remarks

"If they go in with blinders on, they will see what they want to see"

For other examples of delusions prevailing and good sense failing also see, Overnight, Project Grizzly, The White Diamond.