Why Chain of Custody Matters in Drug Cases: People v. Guanzon

In drug cases, the prosecution must prove not only that the accused sold or possessed illegal drugs, but also that the drugs presented in court are the very same items seized from the accused. This is the essence of the chain of custody rule. In People v. Guanzon (G.R. No. 233653, September 5, 2018), the Supreme Court reversed a conviction because the police failed to establish this chain, underscoring that doubts on the identity and integrity of seized drugs lead to acquittal.

The Case: A Buy-Bust Operation in Antipolo

Ricardo Guanzon was arrested in July 2003 after a buy-bust operation in Antipolo City. Police claimed he sold shabu to a poseur-buyer and that another sachet was recovered from his body. He was charged with illegal sale and illegal possession of dangerous drugs under Sections 5 and 11 of Republic Act No. 9165 (the Comprehensive Dangerous Drugs Act of 2002). The trial court convicted him, and the Court of Appeals affirmed. Guanzon appealed to the Supreme Court.

The Issue: Did the Prosecution Prove an Unbroken Chain?

The central question was whether the prosecution had established the chain of custody of the seized drugs beyond reasonable doubt, despite the police's admitted non-compliance with Section 21 of RA 9165, as amended by RA 10640. Section 21 requires the apprehending team to conduct a physical inventory and photograph the seized items immediately after seizure, in the presence of the accused or his representative, an elected public official, and a representative of the National Prosecution Service or the media.

The Ruling: Gaps in Custody Mean Acquittal

The Supreme Court found the prosecution's evidence fatally flawed. The testimonies of two police officers directly contradicted each other on who had possession of the confiscated drug from the arrest site to the police station. One officer said he turned it over to the team leader; the team leader said the officer kept it. No one clearly testified on the handling of the "bought" drug after the arrest. The marking of the drugs—the first link in the chain—was also not clearly established: the place, time, and author of the markings were uncertain, and the accused was not present during marking.

The Court emphasized that marking must be done immediately upon seizure, in the presence of the accused, to prevent switching, planting, or contamination of evidence. Because the first two links of the chain were broken, the Court saw no need to examine the rest. The prosecution also failed to justify its non-compliance with Section 21 or to present inventory and photographs. The Court ruled that the presumption of innocence must prevail where the identity and integrity of the corpus delicti—the illegal drug itself—are in doubt. Guanzon was acquitted.

Practical Takeaways

• Chain of custody is not a technicality. The prosecution must prove every link: seizure and marking, turnover to the investigating officer, turnover to the forensic chemist, and submission to court.
• Marking must be immediate and witnessed. The apprehending officer or poseur-buyer should mark the seized items in the presence of the accused, ideally at the place of arrest or the nearest police station.
• Non-compliance requires justification. If police fail to follow Section 21 of RA 9165, the prosecution must explain the justifiable grounds and show that the integrity of the drugs was preserved.
• Inconsistent police testimony is fatal. Contradictions on who held the drugs from arrest to station create reasonable doubt on whether the drugs presented are the same ones seized.
• For the accused, this ruling is a shield. Where the prosecution fails to prove an unbroken chain, the accused is entitled to acquittal, regardless of other evidence.

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