Mourners march with slain drug suspect Kian Delos Santos' family during his funeral on August 26, 2017 Jonathan Cellona, ABS-CBN News

MANILA (3RD UPDATE) - Three policemen were found guilty of murder for the August 2017 slay of Kian Loyd Delos Santos, an incident that triggered public outcry and scrutiny of President Rodrigo Duterte's war on drugs.

Police officers Arnel Oares, Jeremias Pereda and Jerwin Cruz were sentenced to reclusion perpetua, or 20 to 40 years in prison. They were, however, acquitted from charges of planting evidence.

LOOK: Caloocan RTC declares suspects PO3 Arnel Oares, PO1 Jeremias Pereda and PO1 Jerwin Cruz guilty of murder, with a penalty of Reclusion Perpetua pic.twitter.com/FS6wh27mw9 — Angel Movido (@angelmovido) November 29, 2018

Delos Santos' family rejoiced after the court victory.

"Masaya kami kasi nakuha namin 'yung hustisya para kay Kian (We are happy because we got justice for Kian)," said the teen's uncle, Randy Delos Santos.

Public Attorney's Office (PAO) chief Persida Rueda-Acosta, whose office helped Delos Santos' family during the trial, welcomed the ruling, saying "there is rule of law, truth and justice in the Philippines."

"If ever there are some bad elements doing EJKs (extrajudicial killings), they will face the strong arm of the law. This proves this government does not condone any killing which is unjustifiable," she said.

The three police officers will be committed to the national penitentiary, the New Bilibid Prison, in Muntinlupa City, Justice Secretary Menardo Guevarra said.

Delos Santos' death prompted government action against alleged irregularities in the drug war.

Two months after his slay, President Rodrigo Duterte transferred the leadership of his war on drugs from the Philippine National Police to the Philippine Drug Enforcement Agency.

Delos Santos' case also sparked a Senate investigation into the anti-drug campaign.

TINGNAN: Dispositive portion ng 35-pahinang desisyon ni Caloocan RTC-125 Judge Rodolfo Azucena Jr na naghahatol kina PO3 Arnel G. Oares, PO1 Jeremias T. Pereda, at PO1 Jerwin Cruz na guilty sa murder dahil sa pagpatay kay Kian delos Santos noong Aug 16,2017. pic.twitter.com/xKjDjJ9NZx — Dexter Ganibe (@dzmmRP45) November 29, 2018

Police involved in the operation had said Delos Santos was shot for resisting arrest. But surveillance footage showed the teenager was dragged into a dark alley.

Several witnesses also said they saw some policemen hand Delos Santos a gun, and told the teenager to run before firing shots at him.

Autopsy results showed that Delos Santos sustained fatal gunshot wounds to the head while he was already on the ground kneeling and turning away from police. Delos Santos' family also denied allegations that he served as a drug runner.

Philippine National Police chief Director General Oscar Albayalde earlier said the 3 policemen accused of killing Delos Santos were dismissed.

The Department of Justice, meanwhile, had earlier cleared Chief Insp. Amor Cerill, station commander at the time of Delos Santos' death, in the case.

The then Caloocan City police chief, Senior Supt. Chito Bersaluna, was reassigned to Bulacan province.

Justice Secretary Menardo Gueverra said the 3 officers' conviction "debunks the myth that there is a culture of impunity in the government's war against drugs."

"Not sure if this is the first conviction, but what I can say is that we will continue to dispense justice, and let the hammer fall where it should fall," he said.

The 3 police officers will not be able to apply for parole or a shortened service of sentence on account of good behavior because the court judgment expressly prohibited it, said Guevarra.

However, this could be modified by the Court of Appeals or other higher courts, he said.

“We, of course, expect that the accused will have to appeal. Otherwise, they go straight to prison,” he said.

-- reports from Dexter Ganibe and Mike Navallo, ABS-CBN News