In Florida, all persons are presumed sane and, therefore, it is an affirmative defense that at the time of the commission of the offense the defendant was insane. Florida law requires that the defendant prove insanity by clear and convincing evidence. Florida follows the M’Naghten test. Fla. Stat. § 775.027. Florida does not allow the defendant to use the irresistible impulse test as a criminal defense
Under the M’Naghten test, the defendant is not guilty if, because of a defect of reason due to a mental disease, the defendant did not know either (i) the nature and quality of the act or (ii) the wrongfulness of the act.
In Florida, voluntary intoxication is not a defense and is inadmissible to show that the defendant lacked the specific intent to commit the offense or that the defendant was insane at the time of commission, except when the consumption, injection, or use of a controlled substance was pursuant to a lawful prescription administered to the defendant by a lawful practitioner