Throw someone in an MRI or whatever. Continuously scan their brain, while their eyes are taped open, and display a changing character on the screen. Meanwhile, play a sound file with someone saying "password" in the background constantly, so diversionary mental tactics won't work.
Soon, the first character of their pass will appear, a part of their brain will respond, and you have the first char. Continue until the entire pass appears, and "despair" alights in their brain.
Success! Drink champagne and rejoice.