Art. 651 When defense of insanity at time of offense is available; method of trial

If someone pleads "not guilty" to a crime, they cannot bring up evidence about being insane or having a mental defect at the time of the crime. That kind of evidence simply won't be allowed in that type of trial.

To argue insanity, a defendant must enter a different plea: "not guilty and not guilty by reason of insanity." When someone enters this combined plea, the court handles both parts at the same time, in one trial. The judge or jury will look at whether the person committed the crime and whether they were legally insane when they did it, all in a single proceeding rather than in separate trials.

This means a defendant has to decide upfront which plea to use. Choosing "not guilty" alone means giving up the chance to argue insanity as a defense. Choosing the combined plea keeps that option open, but it also means both issues get decided together in front of the same judge or jury.