Supreme Court Mandates Uniform Chain-of-Custody Protocols for DNA Evidence – Commentary on “Kattavellai @ Devakar v. State of Tamil Nadu” (2025 INSC 845)

1. Introduction

In a landmark judgment delivered on 15 July 2025, a three-judge Bench of the Supreme Court (Vikram Nath, Sanjay Karol and Sandeep Mehta, JJ.) set aside the conviction and death sentence of Kattavellai @ Devakar, accused of the rape-cum-double-murder of two college students at Suruli Falls in 2011. The decision extends far beyond the fate of one appellant; the Court has, for the first time, formulated binding nationwide directions on how police, medical and forensic authorities must collect, preserve and present DNA evidence. Additionally, while stopping short of granting monetary relief, the Court flagged the possibility of compensation for “clean-acquitted” under-trials who spend years in custody because of investigative lapses.

2. Summary of the Judgment

Allowing Criminal Appeal No. 1672/2019, the Court acquitted the appellant of all charges (Sections 302, 376, 379 IPC) and ordered his immediate release.
The entire prosecution rested on circumstantial evidence: “last seen”, extra-judicial confession, recoveries under Section 27 Evidence Act, DNA match, motive and a test-identification-parade (TIP).
The Bench found serious infirmities in each circumstance; most crucially, the chain of custody for vaginal swabs and the accused’s semen sample was “gaping” and unexplained, rendering the DNA report unreliable.
Holding the investigation “faulty” and the trial courts’ reliance on weak evidence unjustified, the Bench reiterated that an accused can be convicted on circumstantial evidence only when all circumstances form a chain wholly inconsistent with innocence (Sharad Birdhichand Sarda principles).
Invoking Article 21, the Court lamented prolonged incarceration of under-trials later found innocent, quoted V. Senthil Balaji (2024), and urged legislative consideration of a statutory compensation scheme.
New Precedent: The Court laid down four mandatory nationwide directions for collection, storage and documentation of DNA samples, including a chain-of-custody register and 48-hour dispatch rule, to be circulated to all High Courts, DGPs and Police Academies.

3. Analysis

3.1 Precedents Cited & Their Influence

Sharad Birdhichand Sarda v. State of Maharashtra (1984) – Panchsheel test for circumstantial evidence; Court held prosecution failed on each limb.
Hanumant v. State of M.P. (1952) reiterated for “fully established circumstances”.
Bodhraj v. State of J&K, Nizam v. State of Rajasthan, etc. – to emphasise caution while applying “last-seen” theory.
Bijender v. State of Haryana (2022) – on the evidentiary fragility of Section 27 recoveries; adopted for doubting weapon/jewellery recovery.
Anil v. State of Maharashtra (2014) – stressed need for strict protocols in DNA handling; became springboard for new directions.
V. Senthil Balaji v. ED (2024) – quoted for prospective compensation discourse.

3.2 Core Legal Reasoning

Last-Seen Evidence Unreliable: Star witness (PW-5) kept silent for 6 days; behaviour not “that of a reasonable man”. Second witness (forest guide) merely saw accused with a sickle, unsurprising for a coconut-cutter.
Arrest & Confession Clouded: Arrest based on vague “suspicion”; no independent witness at arrest; two police confessions recorded, second inexplicably one year later; both hit by Sections 25–26 Evidence Act.
Section 27 Recoveries: Sickle never sent for FSL; clothes untested; gold chain of common design. Recovery therefore lacked “unimpeachable” character.
DNA Evidence Collapse:
- 41-day unexplained delay in sending swabs from hospital to FSL.
- Conflicting testimonies on custody (doctor, constables, IOs each different).
- Semen sample route ambiguous; return from FSL unexplained.
- Court concluded possibility of contamination could not be ruled out & discarded the DNA match.
No Proven Motive: Other valuables missing; gold chain link doubtful; prosecution failed to exclude alternative suspects named by victim’s father.
TIP Tainted: PW-5 had already seen accused at police station and via media; thus dock identification not corroborative.

3.3 Impact Assessment

The judgment is poised to reshape criminal investigation and trial practice in at least three ways:

Standardised DNA Protocol: Directions fill a vacuum – until now, only disparate SOPs existed. The 48-hour dispatch rule and obligatory chain-of-custody register will likely feature in every trial henceforth; non-compliance may make DNA inadmissible.
Heightened Scrutiny of Circumstantial Cases: Trial courts have been cautioned against relying on weak “last-seen”, belated TIPs and unverified recoveries, especially in capital cases.
Debate on Compensation for Wrongful Incarceration: Though left to Parliament, the Court’s strong language could spur legislative or judicial initiatives, akin to U.S. “Innocence Compensation” statutes.

4. Complex Concepts Simplified

Chain of Custody: A real-time log documenting every person who handles evidence from collection to courtroom; akin to parcel tracking, ensuring no tampering.
Section 27 Evidence Act: Allows only that part of a police-custody confession which leads to discovery of a fact to be proved; rest remains inadmissible.
“Last-Seen” Theory: If accused is the last person seen with deceased within a narrow time gap, burden shifts to him to explain; considered a weak circumstance needing corroboration.
Test Identification Parade (TIP): Pre-trial procedure where witness is asked to pick out the suspect from a line-up; helps police test investigation; not substantive evidence.
Clean Acquittal vs. Benefit of Doubt: Clean acquittal = prosecution case fails completely; benefit-of-doubt = Court unsure but gives accused the edge; former has stronger moral case for compensation.

5. Conclusion

“Kattavellai @ Devakar” is a cautionary tale of how investigative slippages can derail justice and jeopardise lives. By exonerating the appellant after 14 years of litigation and custody, the Supreme Court has:

Reaffirmed the indispensable safeguards governing circumstantial evidence, confessions and identification.
Issued the first pan-India, court-mandated DNA Chain-of-Custody Protocol, binding on all police forces and forensic labs.
Opened the door to a future statutory right to compensation for prolonged wrongful incarceration.

The judgment thus serves a dual purpose: rectifying an individual miscarriage of justice and institutionalising systemic reform to prevent recurrence. Its legacy will likely be felt both in police training manuals and in policy debates on the human cost of wrongful prosecution.