When Evidence Is Tainted: Marking Seized Drugs and the Chain of Custody Rule

In every criminal case, the prosecution must prove guilt beyond reasonable doubt. In drug cases, this means proving not just that the accused possessed an illegal substance, but that the very substance presented in court is the same one seized from the accused. The Supreme Court, in Calahi v. People (G.R. No. 195043, November 20, 2017), showed how a simple lapse—failing to mark seized drugs immediately—can break the chain of custody and result in acquittal.

The Facts of the Case

On the evening of November 20, 1997, police officers from the Criminal Investigation and Detection Group (CIDG) were serving a search warrant in Cabanatuan City when they noticed a parked jeepney. Approaching it, they saw four men inside what appeared to be a drug session. The officers arrested the men and confiscated an aluminum foil, an improvised tooter, a lighter, and a white substance later identified as shabu weighing 0.36 gram.

The four accused were charged with illegal possession and use of dangerous drugs under Section 16, Article III of Republic Act No. 6425, the Dangerous Drugs Act of 1972. One accused pleaded guilty; the other three—Arnel Calahi, Enrique Calahi, and Nicasio Rivera—pleaded not guilty and stood trial.

The Regional Trial Court convicted all three, and the Court of Appeals affirmed. The petitioners elevated the case to the Supreme Court, arguing that the prosecution failed to establish the integrity of the seized drugs.

The Issue: Was the Chain of Custody Broken?

The central question was whether the prosecution had proven beyond reasonable doubt that the shabu presented in court was the same substance seized from the petitioners. The defense pointed out that the arresting officers failed to mark the seized items immediately after confiscation, as required by Dangerous Drugs Board Regulation No. 3, series of 1979, as amended.

The prosecution argued that noncompliance with the regulation was a matter between the Dangerous Drugs Board and the arresting officers, and that the presumption of regularity in the performance of official duties should apply.

The Ruling: Acquittal for Failure to Mark Seized Drugs

The Supreme Court ruled in favor of the petitioners and acquitted them. The Court emphasized that in drug cases, the seized drug is the corpus delicti—the body of the crime. Because narcotic substances are not readily identifiable and are susceptible to tampering, substitution, or contamination, the prosecution must establish a complete chain of custody.

Marking is the starting point. The Court held that marking the seized item immediately after seizure is the first link in the custodial chain. It serves to separate the evidence from all other similar items and prevents switching, planting, or contamination. In this case, the records showed no evidence that the seized items were marked upon confiscation. The arresting officer's testimony only showed that the items were brought to the police station and later submitted for laboratory examination—not that they were marked.

The presumption of regularity was rebutted. While the Court has relaxed the strict application of rules in some cases, it requires that the integrity and identity of the drug be preserved. Here, the lack of marking created a gap in the chain of custody, raising reasonable doubt as to whether the specimen presented in court was the same one seized from the petitioners.

A telling inconsistency. The Court also noted a discrepancy in the laboratory findings. The aluminum foil, which the officers claimed contained shabu residue from an ongoing session, tested negative for shabu. The Court found it puzzling that if the petitioners were indeed caught mid-session, the residue in the foil would not match the substance allegedly seized. This further undermined the prosecution's case.

Practical Takeaways

• Marking is mandatory and immediate. Law enforcement officers must mark seized drugs at the scene of seizure, in the presence of the accused if possible. This is the critical first step in the chain of custody.
• The chain of custody must be complete. Every link—from seizure to laboratory examination to presentation in court—must be accounted for. Each handler should testify on how the item was received and what precautions were taken to preserve its integrity.
• Presumption of regularity is not automatic. The presumption that officers performed their duties regularly can be rebutted by showing gaps or irregularities in the handling of evidence, especially the failure to mark seized items.
• For the accused, raise chain-of-custody issues early. If the prosecution fails to establish the identity and integrity of the seized drugs, the case may fail on reasonable doubt, regardless of the weakness of the defense.

This article is general information and not legal advice. For your specific situation, consult a lawyer or ask ASG Legal AI.