Mistake of fact is an exception to criminal liability and one of the five general defenses used to avoid liability of criminal nature for an offence under the Indian Penal Code. An act under the purview of “Mistake of fact” results from mistaken facts of the situation. The facts of each case determine whether the said act is an offense or not.
Mistake of law means mistake as to what law is as well as mistake as to the existence of law on a particular subject.
Mistake of fact
The mistake resulting in the person committing an illegal act from a wrongful understanding by someone as to the facts of a situation is a mistake of fact.
Where the mistaken belief if it were true mistake of fact is a defense to a crime as it would negate a mental state, which is an element of crime. 
The person can use a mistake of fact as an exception in eliminating or reducing the liability. Intentional mistakes cannot escape his liability. To the action of tort Mistake, whether of fact or of law in general is not a defense.
S. 76 in the Indian Penal Code – “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 a mistake of law in good faith believes himself to be, bound by law to do it.”
S. 79 states that “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”
It may be analyzed as –
o A person doing an act bound by law; or
o A person doing an act who believing himself to be bound by law;
o Reason of mistake of fact must be the belief and not reason of mistake of law;
o Must be bona fide belief in good faith;
One may plead in defense if the above conditions are fulfilled to any prosecution for any offense.
Mistake of fact as defense
Mens Rea necessary to constitute a crime is absent when an act is done by reasons of mistake of fact.
When responsible enquiry would get the true state of facts.
When without reference to the mind of the wrongdoer the act is penalized by statute.
In R v Tolson, held that a bona fide belief on reasonable grounds is a good defense to the charge. The accused had married within seven years of marriage after she had been deserted by her husband. She was convicted of bigamy. She in good faith believes on reasonable grounds that her husband was dead. It was considered a defense and she was acquitted.
In The State of Maharashtra v. Mayer Hans GeorgeA can take the ground of a bona fide intention or good faith as a defense in the mistake of fact. A is an officer of the court. Court ordered him to arrest Y. A arrested Z, as he believes Z to be Y.
In Keso Sahu v. Saligram Shah, the accused believing that the offence of smuggling rice was going on in the plaintiff’s house in good faith brings the cart and Cartman to the police station. The suspicion was proved wrong. The accused took the defense of mistake of fact as the act is done in good faith believing it to be justified by law.
In Dhaki Singh v. State, as the act done by him was not justified the accused cannot take the defense of mistake of fact. The accused, mistaking him to be a thief, shot an innocent person although he believes that he is bound to nab the thief. The officer fired at him though he was not in the position to apprehend him.
Mistake of Law
Asking for the defense that a person does not know the law when he commits any tort is not considered as a defense.
The mistake of law is not considered as a defense in IPC as well as in tort as every person knows the law of the country. ‘Ignorance of law is no excuse’ is a principle implying that a wrongdoer to avoid any liability cannot plead ignorance of law as a defense. Hence, unlike mistake of fact a mistake of law even if done in good faith cannot operate as an exonerating factor.
A defendant committed a crime because of a misunderstanding of the law not having the proper mental state.
However, mistake of law can be used as a defense in certain limited circumstances:
o When the law has not been published;
o When the statute or law that was later deemed unconstitutional or overturned relied by defendant;
o A judicial decision that was later overruled when the defendant relied upon;
o An interpretation by an applicable official was relied on.
There are exemptions to avoid his criminal liability –
The act done with due care and proper attention is good faith. The genuine beliefs of a person are also included. The accused has the burden of proof to take the benefit of good faith.
Believed to be justified by the law in good faith
When he acts in good faith with good intention believing that his act is justified by law a person can take the defense.
Ignorantia facti excusat
The legal principle meaning ignorance of fact is an excuse. The accused may be excused in certain cases where by mistake of fact an illegal act may have been committed. However, mistakes of law are not excused. He is still completely liable for the crime, if without the knowledge that the possession or sale of illicit substance is illegal a person sells an illicit substance.
--  Strictlylegal, https://strictlylegal.in/what-is-mistake-of-fact-and-why-is-it-a-defence-under-ipc-free-course/#:~:text=Section%2076%20in%20The%20Indian,by%20law%20to%20do%20it. (Last visited Jun. 18, 2022)  Parshav Gandhi, The Mistake of Fact and Mistake of Law as a Defense, iPleaders (Jun. 18, 2022, 2:08PM), https://blog.ipleaders.in/mistake-fact-mistake-law-defence/  The Indian Penal Code, 1860, § 76, No. 45, Acts of Parliament, 1860 (India)  The Indian Penal Code, 1860, § 79, No. 45, Acts of Parliament, 1860 (India)  Strictlylegal, https://strictlylegal.in/what-is-mistake-of-fact-and-why-is-it-a-defence-under-ipc-free-course/#:~:text=Section%2076%20in%20The%20Indian,by%20law%20to%20do%20it. (Last visited Jun. 18, 2022)  R v Tolson, (1889) 23 QBD 168.  The State of Maharashtra v. Mayer Hans George, 1965 AIR 722. Keso Sahu v. Saligram Shah, 1977 CriLJ 1725.  Dhaki Singh v. State, AIR 1955 All 379.  Parshav Gandhi, The Mistake of Fact and Mistake of Law as a Defense, iPleaders (Jun. 18, 2022, 2:08PM),https://blog.ipleaders.in/mistake-fact-mistake-law-defence/  Sofia Bhambri, MISTAKE OF FACT AND MISTAKE OF LAW, sbhambriadvocates (Jun. 18, 2022, 3:00 PM), https://www.sbhambriadvocates.com/post/mistake-of-fact-and-mistake-of-law  Shouse California Law Group, https://www.shouselaw.com/ca/defense/legal-defenses/mistake-of-law/ (Last visited Jun. 18, 2022)  Maanas Tumuluri, Mens Rea And Actus Reus – Essentials Of A Crime, ipleaders (Jun. 11, 2022, 8:00 PM) Mens Rea And Actus Reus - Essentials Of A Crime - iPleaders
This article is written by HARSHA C of PES UNIVERSITY.