Almost everything the public believes about the insanity defense is wrong, and the far more common issue in criminal court has nothing to do with insanity at all. This article explains how mental illness actually operates in a criminal case. It separates competency, which is about the present, from insanity, which is about the past, and explains why the first arises hundreds of times more often than the second. It covers the constitutional floor for competency, what happens during restoration and how long a person may be held, when the state may medicate a defendant against their will to make them triable, the insanity tests and what a successful verdict actually produces, the special rules for intellectual disability, competency to be executed, and the right to an expert.