From Longman Dictionary of Contemporary Englishstate trooperˌstate ˈtrooper noun [countable] SCPa member of a police force that is controlled by one of the US state governments, who works anywhere in that state
Examples from the Corpus
state trooper• Clinton used a state trooper to lure her to a hotel room during a state-sponsored event in 1991.• Violanti, a former state trooper, is a professor of criminal justice at Rochester Institute of Technology. 