FACTS:

The accused, Roselle Santiago y Pabalinas (alias Tisay), was charged with violations of Section 5 and Section 15 of Republic Act (R.A.) 9165 before the Regional Trial Court (RTC) of Makati City in two separate criminal cases. Initially, Roselle pleaded not guilty in the case involving Section 15 but later changed her plea to guilty. The court deferred her sentencing until the termination of the case for violation of Section 5.

During the pre-trial, the parties stipulated certain facts, including the investigation conducted by PO3 Leo Gabang and the examination of the seized specimen by P/Insp. Richard Allan Mangalip, a forensic chemist of the Philippine National Police (PNP) Crime Laboratory. PO1 Voltaire Esguerra testified that he conducted a test buy from Roselle and later arrested her in a buy-bust operation. The seized sachets were confirmed to contain shabu, and Roselle was found positive for the use of shabu.

Roselle denied selling shabu and claimed mistaken identity as her defense. The RTC found her guilty and sentenced her to life imprisonment and a fine. The Court of Appeals affirmed the conviction, prompting her appeal to the Supreme Court.

The issues presented to the Court are whether the arrest of Roselle was valid and whether the prosecution's evidence established her guilt beyond reasonable doubt. The Court held that Roselle waived the issue of the legality of her arrest by raising it only during appeal. Moreover, the prosecution failed to establish the chain of custody and preservation of the seized substance, rendering their evidence insufficient to prove Roselle's guilt. Thus, the Court reversed the decision of the Court of Appeals and acquitted Roselle.

ISSUES:

1. Whether or not the police conducted a valid arrest in Roselle's case.

2. Whether or not the CA erred in affirming the RTC's finding that the prosecution evidence established her guilt of the offense charged beyond reasonable doubt.

RULING:

1. Roselle waived any question as to the legality of her arrest because she raised the issue only during appeal and not before she was arraigned.

2. The prosecution failed to establish the chain of custody of the seized substance and its preservation from possible tampering. The prosecution also failed to account for the whereabouts of the seized specimen after the crime laboratory conducted its tests. Therefore, the Court finds it difficult to sustain the conviction of Roselle for violation of Section 5 of R.A. 9165.

PRINCIPLES:

• Waiver of the questioning the legality of arrest if not raised before arraignment.

• The prosecution has the burden of establishing the chain of custody of seized evidence to ensure its integrity and prevent tampering.