Chunni Bai v. State of Chhattisgarh (2025): The Supreme Court’s Mandate to Trial Courts to Actively Probe Mens Rea and Mental Capacity under Section 165 Evidence Act

1. Introduction

The Supreme Court’s decision in Chunni Bai v. State of Chhattisgarh, 2025 INSC 577 is remarkable for two interconnected reasons:

It recalibrates the fine line between murder (Section 302 IPC) and culpable homicide not amounting to murder (Section 304 IPC) by emphasising the prosecution’s continuing burden to prove intention beyond reasonable doubt, even where homicidal conduct is undisputed.
It lays down a positive duty on trial courts to employ their powers under Section 165 of the Indian Evidence Act, 1872 to explore an accused’s mental state whenever the circumstances appear “bizarre, unexplained or indicative of impaired capacity,” especially where the accused invokes an eccentric plea such as being under an “invisible power.”

The appellant, Chunni Bai, a rural Anganwadi worker, was convicted by the Trial Court and the High Court for murdering her two minor daughters with an iron crowbar. The Supreme Court upheld the finding that she caused the deaths but found the evidence insufficient to establish the requisite mens rea for murder. Consequently, her conviction was downgraded from Section 302 to Section 304 Part II IPC, and she was ordered to be released having served nearly ten years in custody.

2. Summary of the Judgment

The Court accepted the prosecution’s evidence on actus reus—the appellant undeniably inflicted fatal injuries on her children.
However, it held that the prosecution failed to prove intention or conscious knowledge necessary for Section 302, largely because:
(a) There was total absence of motive.
(b) Witnesses described her frantic cries, lack of flight, and immediate remorse.
(c) She raised a plea—however inarticulate—suggesting mental disturbance (“influence of invisible power”).
The Court emphasised that while the burden of proving an exception (e.g., insanity under Section 84 IPC) lies on the accused (Section 105 Evidence Act), the standard is only preponderance of probabilities, and courts can glean such probabilities from prosecution evidence itself.
Observing serious investigative and judicial omissions in exploring the appellant’s mental state, the Court applied the “third degree” culpable homicide theory (Part II, Section 304) and imposed the sentence already undergone.
In its epilogue, the Court issued important prospective guidelines: Trial judges must, when faced with inexplicable homicides or pleas hinting at mental incapacity, actively question witnesses under Section 165 Evidence Act and not treat motive/intention as an automatic corollary of the killing.

3. Analysis

3.1 Precedents Cited

State of A.P. v. Rayavarapu Punnayya, (1976) 4 SCC 382: Explained the three degrees of culpable homicide, forming the conceptual foundation for downgrading the offence.
Rampal Singh v. State of U.P., (2012) 8 SCC 289: Clarified punishment gradations under Sections 302 and 304; quoted to justify sentencing limits.
Dahyabhai Chhaganbhai Thakkar v. State of Gujarat, AIR 1964 SC 1563: Landmark on the doctrine of burden of proof when insanity is pleaded.
James Martin v. State of Kerala, (2004) 2 SCC 203: Recognised that an accused can rely on prosecution evidence to establish an exception.
Raghunandan v. State of U.P., (1974) 4 SCC 186 and Sidhartha Vashisht (Jessica Lal), (2010) 6 SCC 1: Affirmed the expansive scope of Section 165 Evidence Act empowering judges to elicit truth.

3.2 Court’s Legal Reasoning

Proof of Homicide versus Proof of Murder: The Court separated the undisputed fact of killing from the mental element required for murder. Relying on Punnayya, it reiterated that murder is a special aggravated form of culpable homicide requiring higher mens rea.
Absence of Motive as a Doubt-Creator: Although motive is not a statutory ingredient, its conspicuous absence—especially when the offender is the mother of victims—raised a “reasonable doubt” about her intention.
Plea of Mental Disturbance: The Court accepted that the appellant’s vague reference to an “invisible power” could denote an undiagnosed mental episode. Even without definitive medical proof, this plea, read with behavioural evidence, was enough to dent the prosecution’s burden regarding intention.
Failure of Fact-Finding by Lower Courts: Both the Trial Court and High Court ignored Section 165’s mandate. They did not probe the psychiatric angle or question witnesses on the “invisible power” narrative, thereby overlooking potentially exculpatory circumstances.
Conversion to Section 304 Part II: Applying the “culpable homicide of the third degree” doctrine, the Court held that knowledge of likely death could still be inferred, but not the specific intention required for murder. Hence Section 304 II (up to 10 years) was appropriate.

3.3 Impact of the Judgment

Enhanced Judicial Proactiveness: Trial judges must now actively investigate mental health angles whenever circumstances appear perplexing. Passive recording of evidence is no longer acceptable.
Mens Rea Scrutiny: Prosecutors cannot rely solely on the brutality of the act to prove murder. They must affirmatively establish intention or conscious knowledge, particularly when motive is weak or absent.
Section 165 Evidence Act Revitalised: The decision elevates Section 165 from a seldom-invoked enabling provision to a judicial obligation in relevant cases.
Potential Rise in Section 304 Conversions: Defence lawyers may increasingly argue for downgrades where mental disturbance or lack of motive can create reasonable doubt about intention.
Interface with Mental Health Law: Though Section 84 IPC remains intact, courts may now be more open to acknowledging sub-clinical or temporary mental conditions—even short of legal insanity—to negate murderous intention.

4. Complex Concepts Simplified

Mens Rea: The mental element or guilty mind required to hold someone criminally liable. For murder, this equals intention to cause death or knowledge that death is almost certain.
Culpable Homicide vs. Murder: Both involve causing death, but murder is a graver subset where the accused had higher intention/knowledge. If intention is absent or reduced, the offence may drop to culpable homicide not amounting to murder under Section 304.
Section 165 Evidence Act: Empowers judges to ask any question, at any time, to any witness or party—ignoring rules of relevance—to uncover the truth. It is a tool for judicial inquisitiveness.
Section 105 Evidence Act: Places the burden on the accused to prove any “general exception” (e.g., insanity) on a balance of probabilities. But the prosecution must still prove its case beyond reasonable doubt.
Section 84 IPC (Legal Insanity): Provides complete defence if, at the time of the act, the accused was incapable of knowing the nature of the act or that it was wrong/illegal, due to unsoundness of mind.
Part II, Section 304 IPC: Punishes homicide where death is caused without intention but with knowledge that the act is likely to cause death. Maximum 10-year imprisonment.

5. Conclusion

The Chunni Bai ruling is a seminal reminder that criminal liability is as much about the mind as it is about the deed. By converting a conviction from Section 302 to Section 304 II, the Supreme Court underscored that:

The prosecution must always discharge its heavy burden of proving intention beyond reasonable doubt.
When the accused hints—however clumsily—at mental incapacity, courts have a proactive duty under Section 165 Evidence Act to interrogate that possibility.
The absence of an intelligible motive in a familial homicide, especially by a mother, is a powerful indicator that intention may be lacking.
Judicial power is not exhausted by passive reception of evidence; it involves active participation to ensure justice is rooted in truth, not presumptions.

Going forward, this precedent will likely influence trial strategy, investigative diligence, and judicial behaviour in cases involving mental health overtones, thereby enriching Indian criminal jurisprudence with a more nuanced, humane, and evidence-sensitive approach.