of commission of offence?" 39. So far as our criminal law is concerned, the impact of mental illness on the act (commission of offence) of an accused person and his/her ability to comprehend the legal proceedings before the trial Court is dealt with by the P.P.C. and Cr.P.C. There are certain Prison Rules as well which deal with the mental health of under trial prisoners and convicts. 40. In a criminal trial, two situations may possibly arise in relation to mental health of an accused: firstly, his/her state of mind at the time of commission of offence; and secondly, his/her mental condition before the commencement or during the course of trial. For the first situation i.e. mental condition at the time of commission of offence, section 84 of P.P.C. is relevant. Whereas, for the second situation i.e. mental condition of accused before the commencement or during trial, Chapter XXXIV of Cr.P.C, particularly sections 464 and 465 are relevant. 41. Mental condition at the time of commission of offence is considered as an exception (where act though committed yet not treated as offence) under section 84 of P.P.C. which is reproduced as under:"84. Act of a person of unsound mind. 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. " 42. The scope of section 84, P.P.C. and the principles related thereto were discussed in detail by this Court in the case of Khizar Hayat v. The State2. In this case, the Court was seized with a criminal appeal filed by convict against his conviction and sentence of death, with the plea that at the time of commission of the offence, he was insane and suffering from schizophrenia and his case was fully covered under section 84, P.P.C. This Court, while relying upon the interpretation of section 84, P.P.C. in the case of The State v. Balahari Das Sutradhar3, rejected the plea of the convict and, while maintaining his conviction and sentence of death, observed that not every person who is mentally disturbed or is suffering from some mental illness(es) is, ipso facto, exempted from criminal liability. Any person who seeks the benefit of section 84, P.P.C. must prove that at the time of committing the act, he was laboring under such defect of reason as not to know the nature and consequences of the act he was doing. The Court endorsed the principle that every man is presumed to be sane and assumed to possess a sufficient degree of reason to be responsible for his acts unless the contrary is proved. We have carefully examined the law laid down in Khizar Hayat supra as well as in Lal Khan v. The Crown4 and Gholam Yousaf v. The Crown5 wherein the principles relating to a plea under section 84, P.P.C. were dealt with in detail and it was unequivocally held by the Lahore High Court that in relation to a plea of an accused under section 84, P.P.C., the onus to prove the same is on the accused and the correctness or otherwise of the plea shall be decided after looking at the entire material/evidence available on the record. 43. Thus, within the contemplation of section 84, P.P.C., whenever the plea is raised regarding the state of mind of accused at the time of commission of offence,