G.R. No. 229102 . January 29, 2018.
PEOPLE OF THE PHILIPPINES, PLAINTIFF-APPELLEE, V. PHILIP MAMANGON Y ESPIRITU, ACCUSED-APPELLANT.

FACTS

This case stemmed from two Informations charging accused-appellant Philip Mamangon with illegal sale and illegal possession of dangerous drugs. The prosecution alleged that based on a tip, a buy-bust operation was conducted on February 20, 2009, in Tondo, Manila. PO3 Erick Guzman, as poseur-buyer, successfully purchased a plastic sachet of shabu from Mamangon. Upon arrest, another sachet was recovered from Mamangon’s pocket. The seized items were marked at the scene, inventoried, and photographed at the police station in the presence of Mamangon and arresting officers, then submitted to the crime laboratory, where they tested positive for methylamphetamine hydrochloride.
Mamangon denied the charges, claiming he was arbitrarily apprehended by a police officer he knew the previous day for “verification,” detained overnight, and only presented with the drugs the following day for photographing. He asserted he did not know PO3 Guzman prior to the trial. The Regional Trial Court convicted Mamangon, a ruling affirmed by the Court of Appeals, prompting this appeal.

ISSUE

Whether the Court of Appeals erred in affirming Mamangon’s conviction despite alleged non-compliance with the chain of custody requirements under Section 21, Article II of Republic Act No. 9165 .

RULING

The Supreme Court acquitted Mamangon due to the prosecution’s failure to establish an unbroken chain of custody, which compromised the integrity and evidentiary value of the seized drugs. The legal logic centers on the imperative of proving the identity of the corpus delicti in drug cases. While the buy-bust team marked the items at the scene and conducted an inventory at the police station, they unjustifiably failed to secure the presence of the required witnesses—an elected public official, a representative from the National Prosecution Service, or the media—during the inventory and photographing as mandated by law.
The Court emphasized that the presence of these insulating witnesses is crucial to prevent planting, switching, or contamination of evidence. The prosecution offered no justifiable ground for this deviation, merely stating that no barangay officials were available at the hall, without demonstrating earnest efforts to secure their presence elsewhere. This procedural lapse created reasonable doubt as to whether the drugs presented in court were the same ones seized from Mamangon. His defense of denial, while weak, gains significance in light of the broken chain of custody. Consequently, the presumption of regularity in the performance of official duty was overturned, leading to his acquittal.