As Mercer County's Sheriff, John A. "Jack" Kemler brings with him a law enforcement background that spans three decades." In 1983, Jack started his police career as a patrol officer working for the Trenton Police Department. His assignments included stints as a K-9 handler, narcotics officer and a detective in the Criminal Investigation Bureau. In 1998, Jack was promoted to Sergeant and was assigned to Criminal Investigation Bureau, where he supervised the Violent Crimes Squad.

Throughout his career, Jack has received numerous awards and accommodations, but is most proud of being selected the Trenton Kiwanis' Officer of the Year in 1990. This annual award is presented to the officer that most exemplifies professionalism and valor and is given by his and her fellow officers.

In December 2002, Jack was appointed Chief Sheriff Officer of the Mercer County Sheriff's Office. During his eight years at the Sheriff's Office, Jack has also held the titles of Chief Warrant Officer and Undersheriff and has overseen all aspects of the Office.

As Sheriff, Jack will continue to carry out the agency's primary function of being the law enforcement arm of the Superior Court, continue providing valuable law enforcement assistance to the local police agencies and maintain the many worthwhile community programs afforded to all Mercer County residents provided by the Sheriff's Office.