Final answer:
Patty Hearst used an insanity defense, arguing her participation in crimes during captivity was due to brainwashing imposing a state of diminished capacity.
Step-by-step explanation:
Patty Hearst claimed that her seemingly willing participation in the Symbionese Liberation Army's crimes was due to brainwashing she experienced while in captivity. The category of defense she was using is known as an insanity defense, commonly understood in legal terms to refer to a defense by excuse in a criminal case, arguing that the defendant is not responsible for their actions due to an episodic or persistent psychiatric disease at the time of the criminal act.
This defense can take various forms, one of which is the claim that the defendant was in a state of diminished capacity, as Hearst's defense claimed that her mental state, due to the brainwashing, impaired her ability to understand the criminality of her actions.