Introduction

Deoxyribonucleic Acid (DNA) has emerged as a crucial tool in modern criminal investigations, offering precision in identifying perpetrators and linking evidence. However, lapses in collection, preservation, and analysis have often compromised its reliability in Indian courts. Recognising these systemic gaps, the Supreme Court in Kattavellai @ Devakar v. State of Tamil Nadu issued detailed guidelines to ensure the integrity of DNA evidence.

Why Intervention Was Needed

1. Case Background

   • The Devakar case involved rape, murder, and robbery.

   • Vaginal swab samples were delayed in reaching the Forensic Science Laboratory (FSL).

   • Chain of custody could not be established, raising the risk of contamination.

2. Lapses Noticed by Court

   • Absence of uniform guidelines across states.

   • Delays in sending DNA samples to FSLs.

   • Inadequate documentation and weak accountability in the chain of custody.

3. Rationale

   • Though “Police” and “Public Order” are state subjects, the Court invoked its constitutional authority to ensure uniformity across the nation.

Supreme Court Guidelines on DNA Samples

1. Proper Documentation

   • DNA collection must be accompanied by detailed records: FIR number, date, statutes invoked, investigating officer’s details, signatures of medical professionals, and independent witnesses.

2. Transportation of Samples

   • Investigating officer responsible for safe and prompt delivery.

   • Samples must reach FSL within 48 hours; delays must be explained.

3. Storage Protocols

   • No sample package to be opened, altered, or resealed without trial court authorisation.

4. Chain of Custody Register

   • Must be maintained until final disposal of the case.

   • Any lapse must be explained by the investigating officer.

Judicial Approach to DNA Evidence

1. Recognition of Validity

   • Anil v. State of Maharashtra (2014): DNA profiles considered valid and reliable, subject to quality control in labs.

2. Concerns on Contamination

   • Manoj v. State of Madhya Pradesh (2022): DNA rejected when collected from open areas, prone to contamination.

3. Issues of Delay and Tampering

   • Rahul v. State of Delhi (2022): DNA reports rejected due to prolonged storage in police custody without safeguards.

4. Opinion Evidence

   • Court reiterated DNA falls under “opinion evidence” (Evidence Act, Section 45 / BSA 2023, Section 39).

   • Its probative value varies case to case and cannot solely secure a conviction.

Importance and Limitations of DNA Evidence

1. Strengths

   • DNA can be extracted from bone, blood, semen, saliva, hair, and skin.

   • High accuracy in establishing biological origins when properly handled.

2. Limitations

   • Risk of contamination if chain of custody is broken.

   • Reliability depends on lab procedure and quality control.

   • DNA alone is insufficient to convict; corroborative evidence is necessary.

3. Legal Position

   • DNA is not substantive evidence but supportive opinion evidence.

   • Must be scientifically and legally proved in each case.

Way Forward

1. Standardisation: Uniform procedures across all states to prevent inconsistency.

2. Capacity Building: More FSLs, trained personnel, and modern infrastructure.

3. Awareness & Training: Police and medical officers must be sensitised to handling biological samples.

4. Judicial Prudence: Courts must assess DNA with caution, ensuring corroboration with other evidence.

5. Balancing Rights: Protecting privacy and ensuring fair trial rights alongside technological use.

Conclusion

DNA is a powerful tool, but its effectiveness depends not merely on technology, but on the integrity of processes surrounding its collection, preservation, and analysis. The Supreme Court’s recent guidelines aim to create uniformity, prevent contamination, and enhance credibility. However, as the Court itself noted, DNA remains an opinion evidence—helpful but not conclusive. For justice to be served, DNA must be seen as part of a holistic evidentiary framework rather than a silver bullet.

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