MANILA (Reuters) - A Philippine court on Thursday sentenced three police officers to up to 40 years in jail for the murder of a 17-year-old high school student, the first to be convicted in President Rodrigo Duterte’s drugs war.

The Caloocan City regional trial court declared the three police guilty for the killing of Kian Lloyd delos Santos in August 2017 in a dark, trash-filled alley in a northern suburb in the capital Manila.

“A shoot first, think later attitude can never be countenanced in a civilized society. Never has homicide or murder been a function of law enforcement. The public peace is never predicated on the cost of human life”, said the ruling by Judge Roldolfo Azucena.

This was the first case of what human rights advocates say was an extrajudicial killing carried out by state-agents in the 29-month war on drugs, which saw close to 5,000 people dead in police anti-drugs operations.

Police reject allegations that the killings were executions, saying the drug peddlers and users were killed in shootouts, and that they were acting in self-defense.

“We respect the decision of the court. We don’t tolerate any erring police officers,” said Benigno Durana, national police spokesman, adding the police force “stand fully behind police officers engaged in the drug war, who are doing their jobs within the bounds of the law”.

The death of the school boy has stirred unprecedented public attention on what activists say are executions and systematic abuses by police backed steadfastly by Duterte. (reut.rs/2jozqDx)

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Duterte, a firebrand leader who unleashed a ferocious war against illegal drugs after coming into office in June 2016, has more than once said he would not allow the police to go to jail for killing drug users and pushers.

But shortly after the verdict was handed down, Duterte’s spokesman, Salvador Panelo said: “This is murder, there is intention to kill. The president would never tolerate that”.

Duterte’s government has repeatedly said there was no declared policy to kill drug users and pushers.

“The conviction of the three police officers for murdering Kian delos Santos is a victory for justice but it is not enough. The killings must stop,” said Jose Manuel Diokno, chairman of the Free Legal Assistance Group (FLAG).

FLAG has questioned the legality of the drugs war before the Philippine Supreme Court.

Delos Santos was found dead in an alley with a gun in his left hand. Police said they killed him in self defense, but his family dismissed that as a lie.

Security cameras showed the officers aggressively escorting a man matching delos Santos’ description in the direction of the spot where he was killed.

“Justice was served for my son,” Kian’s mother, Lorenza delos Santos, told reporters outside the courtroom. “We were able to prove that my son was innocent of all the accusations hurled against him.”

(This story corrects typographical error to say men sentenced to up to 40 years in jail, not 49 years, paragraph one)