Three Philippine policemen were sentenced on Thursday to decades in prison for murdering a teenager during an anti-narcotic sweep, a first conviction of officers carrying out President Rodrigo Duterte's war on drugs.Duterte has vowed to pardon authorities involved in his bloody crackdown, but even he refused to defend the 2017 killing of Kian delos Santos in a dank Manila alley - which helped spark rare protests against the campaign.Police said the 17-year-old was a drug courier who fire