The maxim Ignorantia Juris non excusat, Ignorantia facti excusat, is simple and intelligible enough. It is a general rule of English Law that one must admit that ignorance of law could never be admitted as an excuse but ignorance of fact excuse all liability.
Statutory Framework Regarding Mistake of Fact:
In the Indian Penal Code Mistake of fact and mistake of law have been provided in Section 76 and 79. These two Sections can be conveniently considered together.
“Section 76: Act done by a person bound, or by mistake of fact believing himself bound by Law. Nothing is an offence which is done by a person who is, or who by reason of a mistake of fact and not by reason of mistake of law, in good faith believes himself to be, bound by law to do it.
(a). A, a soldier, fires on mob by the order of his superior officer, in conformity with the commands of the law. A has committed no offence.
(b). A, an officer of a court of justice, being ordered by that Court to arrest Y, and, after due enquiry, believing Z to be Y, arrests Z. A has committed no offence.
“Section 79: Act done by a person justified, or by mistake of fact believing himself justified, by Law: Nothing is an offence which is done by any person who is justified by law, or who by reason of a mistake of fact and not by reason of a mistake of law, in good faith, believes himself to be justified by Law in doing it.
Illustration: A sees Z commit what appears to A to be a murder. A, in the exercise, to the best of his judgment exerted in good faith, of the power which the law gives to all persons of apprehending murders in the fact, seizes Z, in order to bring Z before the proper authorities. A has committed no offence, though it may urn out that Z was acting in self-defence.”
Distinction between Section 76 and Section 79:
section 79 is complementary to Section 76. In fact, Section 79 should have been placed just after section 76 and numbered as Section 77. Section 76 deals with cases where by reason of a mistake of fact the person under a mistake considers himself bound by law to act in a particular way, although on the true state of fact is an offence. Section 79 on the other hand deals with cases where by reason of a mistake of fact the person under such mistake consider himself simply justified by law to act in a particular way. The anti-thesis between the two cases is involved in the words ‘bound by law’ in Section 76 and ‘justified by law’ in Section 79.