The question may arise as to whether a defendant is mentally capable of facing a trial. Defendants cannot be prosecuted if they suffer from a mental disorder that prevents them from understanding the proceedings and assisting in the preparation of their defense.
Based on a defendant's unusual behavior, a judge, prosecutor, or defense attorney may ask that trial be delayed until the defendant has been examined and his or her ability to understand the proceedings has been determined in a court hearing. If a judge finds that a defendant doesn't understand what's going on, the defendant will probably be placed in a mental institution until competence is reestablished. At that time, the trial will be held.
This situation is different from using the insanity defense. For more information on the insanity defense, see How a Defendant's Mental State Affects His or Her Responsibility for a Crime.