Republic Act No. 6425, the original Dangerous Drugs Act, was enacted to consolidate and codify all laws on dangerous drugs. It established the Dangerous Drugs Board and penalized the importation, sale, manufacture, and use of prohibited drugs with severe penalties including life imprisonment and death.

Republic Act No. 7659 amended RA 6425 by reimposing the death penalty for certain drug offenses involving large quantities of dangerous drugs. This was part of the broader restoration of capital punishment in the Philippines after the 1987 Constitution allowed Congress to reimpose it for heinous crimes.

The Supreme Court established the chain of custody rule for dangerous drugs cases, requiring the prosecution to prove every link in the chain from seizure to presentation in court. This landmark ruling emphasized that the identity and integrity of the corpus delicti must be established with moral certainty.

Republic Act No. 9165 repealed RA 6425 and became the governing law on dangerous drugs in the Philippines. It reorganized enforcement agencies, created the Philippine Drug Enforcement Agency (PDEA), strengthened penalties, and introduced comprehensive prevention, treatment, and rehabilitation programs.

The Supreme Court ruled that strict compliance with Section 21 of RA 9165 regarding the custody and disposition of confiscated drugs is mandatory. The physical inventory and photograph must be conducted immediately after seizure in the presence of the accused, media, DOJ representative, and elected official.

The Dangerous Drugs Board amended the Implementing Rules and Regulations to provide that non-compliance with Section 21 requirements may be excused under justifiable grounds, provided the integrity and evidentiary value of the seized items are preserved.

The Supreme Court established the 'saving clause' doctrine, holding that non-compliance with Section 21 may be excused when the prosecution proves justifiable grounds and that the integrity and evidentiary value of evidence were preserved. This relaxed the strict compliance standard.

The Supreme Court clarified that for the saving clause to apply, the prosecution must prove that law enforcement exerted earnest efforts to secure the required witnesses under Section 21. Mere statements of unavailability are insufficient; concrete steps must be demonstrated.

Republic Act No. 10640 amended Section 21 of RA 9165 by reducing the required witnesses from three to two (elected official plus either DOJ or media representative) and clarifying when inventory may be conducted at the nearest police station or PDEA office.

The Supreme Court held that even during the COVID-19 pandemic, law enforcement must substantially comply with Section 21 requirements. Health protocols do not excuse failure to secure required witnesses or document justifiable grounds for non-compliance.

The Supreme Court acquitted the accused due to gaps in the chain of custody, particularly the failure to establish who had custody of the seized drugs between the forensic chemist and the court presentation, reaffirming that every link must be accounted for.