G.R. No. 149152 - Mamangun vs. People

The petitioner, Rufino S. Mamangun, a police officer, was charged before the Sandiganbayan with the crime of Murder under Criminal Case No. 21131.
Subsequent trial proceedings eventually led to a conviction for Homicide after the court determined that the aggravating circumstances necessary to elevate the killing to Murder were absent, while giving due weight to mitigating circumstances such as the incomplete justifying circumstance (acting in the performance of duty) and voluntary surrender.
The decision of the Sandiganbayan was rendered on January 19, 2001 (promulgated February 13, 2001), which formed the basis for the petitioner’s appeal through a petition for review under Rule 45 of the Rules of Court.

On July 31, 1992, at about 8:00 in the evening in Brgy. Calvario, Meycauayan, Bulacan, a robbery-holdup in progress triggered residents’ alarm as a man was heard shouting “Magnanakaw! Magnanakaw!”
The ensuing commotion led several residents to give chase to a suspect who entered the yard of Antonio Abacan’s house and proceeded to the rooftop.
The Meycauayan Police Station, acting on a tip of an ongoing robbery-holdup, dispatched two patrol cars (Patrol Car No. 601 and Patrol Car No. 602) with police officers including petitioner Mamangun, PO2 Diaz, and PO2 Cruz as part of the on-scene response.

Arriving at the scene with the permission of the homeowner, petitioner Mamangun, together with PO2 Diaz and PO2 Cruz, proceeded onto the rooftop armed with drawn handguns to search for the alleged robbery suspect.
On the rooftop, the officers observed a man whom they presumed to be the suspect; as they approached, petitioner Mamangun took the initiative by firing his handgun once.
The man shot turned out to be Gener Contreras, who was unarmed and in the process of uttering “Hindi ako. Hindi ako!” indicating his non-involvement in the crime.
An autopsy conducted by Dr. Benito Caballero revealed that the fatal bullet had entered at the outer left arm, traversed critical areas including the left lung and vertebral column, and that the injury caused shock due to massive hemorrhage leading to Contreras’ death.

Prosecution witness Crisanto Ayson testified that he accompanied the officer team to the rooftop, observed the victim at a distance, and saw petitioner Mamangun point his .45 caliber pistol at Contreras prior to the fatal shot.
According to Ayson, Contreras verbally protested (“Hindi ako, hindi ako!”) before being fatally shot by Mamangun, who retorted “Anong hindi ako?” before firing.

Petitioner Mamangun and his co-policemen (including PO2 Cruz and PO2 Diaz) denied the presence of Ayson on the rooftop and maintained that they were the only ones present amid dark surroundings.
Their account stated that upon chasing a person seen crouching near the water tank—presumed to be the robbery suspect—they encountered a situation where that person (later identified as Contreras) allegedly brandished a stainless steel pipe, prompting Mamangun to shoot on his left arm.
The defense narrative emphasized that Contreras’ supposed use of a steel pipe was an afterthought introduced later to justify the shooting, especially considering that the pipe was only recovered subsequent to a police investigation by Investigator Hernando B. Banez.

After the shooting, petitioner Mamangun reported the incident to the desk officer and subsequently to Police Investigator Banez who went to the scene and recovered a lead pipe—a fact that raised suspicion regarding the timing and consistency of the petitioner’s self-defense claim.
In its decision, the Sandiganbayan found that petitioner Mamangun did not have sufficient evidence to prove that the shooting was a necessary consequence of his duty as a policeman, hence rejecting the claim of complete justification and upholding his conviction for Homicide with mitigating circumstances.

Whether the petitioner’s invocation of the justifying circumstance under paragraph 5, Article 11 of the Revised Penal Code—purporting that the shooting was committed in the performance of his duty as a policeman—could absolve him of criminal liability.
Whether the evidence sufficiently supports the claim of self-defense (or incomplete self-defense) given that the victim, Gener Contreras, was unarmed and had already made a non-admission (“Hindi ako”) before being shot.
The credibility and reliability of the conflicting testimonies between the prosecution’s eyewitness account (by Ayson) and the defense’s account offered by the petitioner and his co-policemen.
Whether the factual findings and conclusions reached by the Sandiganbayan regarding the necessity (or lack thereof) of the petitioner’s violent act, alongside the admission of mitigating circumstances, were supported by the evidence on record.