Background: Attempts to obviate criminal responsibility of insane criminals in law and importance of recognizing the cases involving lack of judgment and volition have made the courts to require expert opinion, including forensics psychiatrists and psychologists, in these cases. By determining the exact criteria in this regard, a considerable number of patients mistakenly convicted will have a chance to be acquitted, and if necessary, referred to mental hospital instead of prison. The present study was aimed to provide a way to converge medical and legal points of view in such cases in order to prevent unwise punishment of these patients.
Methods: The present study is a descriptive - analytic one, carried out through rational and logical reasoning regarding what was available in different resources (including legal, psychologic, psychiatric and forensic medicine texts).
Findings: Insanity is defined in criminal law as the condition of a person lacking judgement and volition to be able to act normally. Although, these psychological and/or psychiatric references don’t mention the term "insanity" and its diagnostic criteria, psychiatric disorders resulting in lack of judgement and volition, might obviate criminal responsibility. Therefore, instances of insanity include degrees of disorders such as schizophrenia, hypomania, mania, depression, delusional disorders, epilepsy, dementia, personality disorders, mental disabilities, etc.
Conclusion: Although the term "insanity" is a legal concept that includes the instances of insanity in legal medicine. It can be said that not only the concepts of insanity, either in psychiatry or in criminal law, do not oppose, but also there are numerous instances of overlapping in these cases.