Context: The Supreme Court has issued uniform guidelines to ensure the integrity of DNA (deoxyribonucleic acid) samples in criminal cases.
Relevance of the Topic: Prelims: Key facts about SC guidelines say on DNA; Applications of DNA profiling.
Importance of DNA evidence in criminal cases:
- DNA is a molecule that encodes the genetic information in all living organisms. It can be obtained from biological materials, such as bone, blood, semen, saliva, hair, or skin.
- Generally, when the DNA profile of a sample found at a crime scene matches the DNA profile of a suspect, it can be concluded that both samples have the same biological origin. However, it is not substantive evidence in criminal cases.
What do SC guidelines say on DNA?
The SC in Kattavellai @ Devakar v. State of Tamil Nadu has issued four guidelines for cases where DNA evidence is involved.
- Collection and documentation: DNA samples must be collected with due care, appropriately packed and labelled (FIR number and date, sections and statutes involved, details of the investigating officer, police station). The document must include the signatures and designations of the medical professional present, investigating officer, and independent witnesses.
- Transportation: The investigating officer must ensure that the samples reach the concerned Forensic Science Lab within 48 hours of collection. The reasons for delay (if any) must be recorded, and samples should be preserved.
- Storage: No package shall be opened, altered, or resealed without express authorisation from the trial court.
- Chain of Custody Register (logbook that tracks DNA sample till the case ends) must be maintained. The investigating officer is responsible for explaining any lapses in compliance.
Need to issue the directions:
- Though some guidelines have been issued by various bodies, there is neither uniformity nor a common procedure to be followed by all investigating authorities.
- ‘Police’ and ‘Public Order’ are subjects mentioned in the State List of the Seventh Schedule of the Constitution, but the SC deemed it necessary to issue these guidelines to have uniformity of procedure.
- Past rulings show that lapses in handling have led to DNA reports being rejected, making both proper collection and quality control essential.
- Unexplained delays in sending DNA samples to the Forensic Laboratory (FSL) can risk the possibility of sample contamination.
Associated Court rulings:
- In Anil v. State of Maharashtra (2014): The SC observed that a DNA profile is valid and reliable, but this depends on quality control and procedure in the laboratory.
- Manoj v. State of Madhya Pradesh (2022): The SC rejected a DNA report on the ground that recovery was made from an open area and the likelihood of its contamination cannot be ruled out. The blood stains found on the articles were disintegrated, and the quantity was insufficient to run any classification test.
- Rahul v. State of Delhi (2022): The DNA evidence was rejected because it remained in the Police Malkhana for two months and during such time, the possibility of tampering could not be ruled out.
- Kattavellai @ Devakar v. State of Tamil Nadu (2025): The SC stated that DNA evidence is in the nature of opinion evidence as envisaged under Section 45 of the Evidence Act. Like any other opinion evidence, its probative value varies from case to case. Therefore, DNA evidence must be proved scientifically and legally.
The investigating agency needs to ensure that samples are collected properly, without contamination, and sent to the FSL without delay.
Also Read: DNA Profling