 The insanity or mental illness or lunacy defense, also known in the criminal trial jurisprudence as the mental disorder defense, is an affirmative defense by excuse in a criminal case, arguing that the defendant or the accused is not responsible for his or her actions due to a sporadic or intermittent or persistent psychiatric disease at the time of the criminal act, at the time of the commission of the criminal act. This is different from an excuse of provocation in which the defendant is responsible but the responsibility is lessened due to a temporary mental state. The oldest reference to the immunity from extensive criminal sentencing or punishment on the ground of mental illness is found in the Code of Hammurabi, a well preserved babylonian code of law of ancient Mesopotamia dated to about 1754 BC. Legal definitions of insanity or mental disorder are varied and include the Managaton Rule, the Durham Rule, the 1953 British Royal Commission on Capital Punishment Report, the Alley Rule which is an abbreviation for the American Legal Institute Model Penal Code Rule and other provisions. Often relating to a lack of mensarea that is guilty mind. In the criminal laws of Australia and Canada statutory legislation enshrined the Managaton Rule with the term defense of mental disorder, the defense of mental illness or not criminally responsible by reason of mental disorder employed. Being incapable of distinguishing right from wrong is one basis for being found to be legally insane as a criminal defense. It originated in the Managaton Rule and has been reinterpreted and modernized through more recent cases such as People vs Saravo, which I would request all the viewers to go through on the internet, People vs Saravo. In the United Kingdom Ireland and the United States, use of the defense is rare. However, since the criminal procedure Insanity and Unfitness to Plead Act 1991, Insanity please have steadily increased in the UK. Meeting getting factors including things not eligible for the Insanity defense such as intoxication or more frequently diminished capacity may lead to reduced charges or reduced sentences. The defense is based on evaluations by forensic mental health professionals with the appropriate test according to the jurisdiction concerned. Their testimony guides the jury or the judges as the case may be, but they are not allowed to testify to the accused's criminal responsibility as this is a matter for the jury to decide. Similarly, mental health practitioners are restrained from making a judgment on the issue of whether the defendant or accused is or is not insane or what is known as the ultimate issue. Some jurisdictions require the evaluations to address the accused or defendant's ability to control their behavior at the time of the commission of the offence. That's important. The volitional limb as it is called. A defendant claiming the defense is pleading not guilty by reason of Insanity or guilty but insane or mentally ill. In some jurisdictions which if successful may result in the defendant being committed to a psychiatric facility for an indeterminate period. Now coming to the Indian set of laws dealing with insanity or lunacy or mental disorder. Section 84 of the Indian Penal Code deals with the criminal act by an unsound person. They said Indian law says that nothing is an offence which is done by a person who at the time of doing it by reason of unsoundness of mind is incapable of knowing the nature of the act or that he is doing what is either wrong or contrary to law. However, interestingly the data I have extracted from one of the research papers of an expert depicts a very different and unique sort of a story. That is that the majority of cases where the insanity defense was taken by the accused under section 84 got to be rejected by several high courts in India. The high courts acquitted the accused under section 84 IPC in less than 20% cases thereby accepting the insanity pleas raised by the accused. Very small percentage. The verdicts of the trial courts rested on the documentary evidence of mental illness prior to the crime. That is very relevant in the Indian context. The documentary evidence of mental illness prior to the crime and the psychiatrist's opinion as well is highly relevant. It is critical to read the associated case laws to ascertain the elements linked with the success or decline of insanity pleas.