A person who is responsible for enforcing the criminal laws of this state or a political subdivision of this state and who is employed or volunteers:
(i) as a peace officer commissioned by a city, university that has established a police department under 352.121 (University police departments and officers) or 353.125 (Creation of police department and commission of police officers), port, school district, mass transit district, county or county service district authorized to provide law enforcement services under 451.010 (Authorization to establish master plans and service districts)
(ii) with the Department of State Police or the Criminal Justice Division of the Department of Justice;
(iii) as an investigator of a district attorney's office, if the investigator is certified as a peace officer in this state; or
(iv) as an authorized tribal police officer