The Criminal Investigation Unit is comprised of  four Detectives, under the direction of   SGT Scott Rupert. The primary function of the Criminal Investigation Section is to conduct criminal investigations of serious crimes or those cases requiring extensive follow up after a complaint has been taken by a Patrol Officer. In addition to their criminal investigative duties, Detectives are also assigned to the Drug investigative unit.

Detectives assigned to the Drug Investigation Unit conduct investigations into the use and sale of illegal narcotics within Mifflin County Regional Police Jurisdiction, and are also assigned to the Mifflin County Drug Task Force to investigate drug sales at the County level.

The detectives work closely with Drug Task Force members, agents from the Federal Drug Enforcement Agency, Attorney General Office, Pennsylvania State Police, US Marshals, FBI and local law enforcement agencies to take a pro-active approach to the war on drugs. Surveillance, undercover operations and the use of informants are some of the methods used to aid in their investigations