Mistake of Law and Mistake of Fact (Sections 76 and 79 IPC)

Introduction

Mistake is an important general defence in criminal law. It applies when a person commits an act under a wrong belief.

The law recognises that a person acting under a genuine mistake of fact may not have a guilty mind (mens rea). However, mistake of law is generally not a valid defence.

Meaning / Definition

Mistake means doing an act or omitting (not doing) an act due to ignorance or wrong belief.

In criminal law:

• A mistake can remove criminal liability if it prevents the formation of guilty intention.
• Courts judge the accused based on the facts he believed to exist, not the actual facts.

Key conditions for defence of mistake:

• The facts believed must, if true, justify the act
• The mistake must be reasonable
• The mistake must relate to fact, not law

The principle is based on the maxim:
“Ignorantia facti excusat, ignorantia juris non excusat”
(Ignorance of fact excuses, ignorance of law does not excuse)

Modes or Types

Mistake of Fact (Section 76 and Section 79 IPC)

Mistake of fact is a valid defence when:

• The accused acts under a wrong belief of facts
• The belief is in good faith (honestly with due care and attention)

Section 76 – Bound by Law

• Applies when a person believes he is legally bound (required by law) to do an act
• Even if the belief is mistaken, he is protected

Example: A police officer arrests a person believing he is required to do so by law

Section 79 – Justified by Law

• Applies when a person believes his act is justified (allowed) by law
• The act is done due to mistake of fact and in good faith

Example: A person uses force believing he has the right of private defence

Key Requirement:

• Good faith (honesty with due care and attention)

Mistake of Law

• Mistake of law is not a defence
• Every person is presumed to know the law

Reason:

• Allowing this defence would encourage ignorance of law
• It would make prosecution difficult

Limited Exceptions

In rare situations, mistake of law may be considered:

• Law was not properly published
• Reliance on a law later declared invalid
• Reliance on a court judgment
• Reliance on official interpretation

Good Faith (Essential Requirement)

• The act must be done with due care and attention
• Mere honesty is not enough

Factors to determine good faith:

• Nature of the act
• Importance of the act
• Opportunity to take care

Important Case Law

• R v. Tolson

  • Accused remarried believing her husband was dead
  • Held: Not guilty due to reasonable mistake of fact

• R v. Prince

  • Accused took a minor believing she was above 16
  • Held: Guilty as he did not act with due care

• State of West Bengal v. Shew Mangal Singh (Supreme Court of India)

  • Police fired on orders of superior officer
  • Held: Protected as act was done in good faith under lawful orders

Distinction / Comparison

Practical Example

A police officer arrests X believing X is a criminal based on wrong information.

• This is a mistake of fact
• If done in good faith, the officer is protected under Section 76

Summary

• Mistake is a defence when it removes guilty intention (mens rea).
• Mistake of fact is a valid defence if done in good faith.
• Sections 76 and 79 IPC protect acts done under mistake of fact.
• Section 76 applies when a person believes he is bound by law.
• Section 79 applies when a person believes he is justified by law.
• Mistake of law is generally not a defence.
• Good faith requires honesty along with due care and attention.