Law undoubtedly presumes that every person committing an offence is sane and liable for his acts, though in specified circumstances it may be rebuttable. The doctrine of burden of proof in the context of the plea of insanity was stated as follows in Dahyabhai Chhaganbhai Thakkar v. State of Gujarat, (1964) 7 SCR 361 :
“(1) The prosecution must prove beyond reasonable doubt that the accused had committed the offence with the requisite mens rea, and the burden of proving that always rests on the prosecution from the beginning to the end of the trial.
(2) There is a rebuttable presumption that the accused was not insane, when he committed the 7 crime, in the sense laid down by Section 84 of the Indian Penal Code: the accused may rebut it by placing before the court all the relevant evidence oral, documentary or circumstantial, but the burden of proof upon him is no higher than that rests upon a party to civil proceedings.
(3) Even if the accused was not able to establish conclusively that he was insane at the time he committed the offence, the evidence placed before the court by the accused or by the prosecution may raise a reasonable doubt in the mind of the court as regards one or more of the ingredients of the offence, including mens rea of the accused and in that case the court would be entitled to acquit the accused on the ground that the general burden of proof resting on the prosecution was not discharged.”
11. Section 84 of the IPC carves out an exception, that an act will not be an offence, if done by a person, who at the time of doing the same, by reason of unsoundness of mind, is incapable of knowing the nature of the act, or what he is doing is either wrong or contrary to law. But this onus on the accused, under Section 105 of the Evidence Act is not as stringent as on the prosecution to be established beyond all reasonable doubts.
The accused has only to establish his defence on a preponderance of probability, as observed in Surendra Mishra vs. State of Jharkhand, (2011) 11 SCC 8 495, after which the onus shall shift on the prosecution to establish the inapplicability of the exception. But, it is not every and any plea of unsoundness of mind that will suffice. The standard of test to be applied shall be of legal insanity and not medical insanity, as observed in State of Rajasthan vs. Shera Ram, (2012) 1 SCC 602, as follows :
“19. ……..Once, a person is found to be suffering from mental disorder or mental deficiency, which takes within its ambit hallucinations, dementia, loss of memory and selfcontrol, at all relevant times by way of appropriate documentary and oral evidence, the person concerned would be entitled to seek resort to the general exceptions from criminal liability.”
12. The crucial point of time for considering the defence plea of unsoundness of mind has to be with regard to the mental state of the accused at the time the offence was committed collated from evidence of conduct which preceded, attended and followed the crime as observed in Ratan Lal vs. State of Madhya Pradesh, (1970) 3 SCC 533, as follows:
“2. It is now wellsettled that the crucial point of time at which unsoundness of mind should be 9 established is the time when the crime is actually committed and the burden of proving this ties on the accused. In D.G. Thakker v. State of Gujarat it was laid down that “there is a rebuttable presumption that the accused was not insane, when he committed the crime, in the sense laid down by Section 84 of the Indian Penal Code, the accused may rebut it by placing before the Court all the relevant evidence – oral, documentary or circumstantial, but the burden of proof upon him is no higher than that which rests upon a party to civil proceedings”.
13. If from the materials placed on record, a reasonable doubt is created in the mind of the Court with regard to the mental condition of the accused at the time of occurrence, he shall be entitled to the benefit of the reasonable doubt and consequent acquittal, as observed in Vijayee Singh vs. State of U.P., (1990) 3 SCC 190.
14. We shall now consider the sufficiency of other medical and defence evidence to examine if a reasonable doubt is created with regard to the mental state of the appellant at the time of commission of the assault on a preponderance of probability, coupled with the complete lack of consideration of the evidence of P.W.14. Merely because an injured witness, who may legitimately be classified as an interested witness for obvious reasons, may have stated that the appellant was not of unsound mind, cannot absolve the primary duty of the prosecution to establish its case beyond all reasonable doubt explaining why the plea for unsoundness of mind taken by the accused was untenable.[ Devidas Loka Rathod Vs. State of Maharashtra –Criminal Appeal No.814 of 2017]