The legal standard for determining mental state at the time of the offense also varies from state to state. Florida's insanity test is a derivation of the M'Naghten test. It holds that an individual is insane when, at the time of the offense, the defendant had a mental infirmity, disease, or defect and, because of this condition, the defendant did not know what he or she was doing or it consequences, or although the defendant knew what he or she was doing and its consequences, he or she did not know that it was wrong. In addition, substance abuse/dependency can only form the basis of an insanity defense in the permanent organic impairment. To this extent, simply being under the influence of alcohol or drugs does not meet the legal standard for insanity.

The mental state at the time of the offense evaluation involves both an interview with the defendant and the consideration of third party information. Offense related information can be obtained from attorney notes, witnesses, victims, confession, preliminary hearing transcripts, autopsy reports, and newspaper accounts.