John "Jack" Kemler's experience in law enforcement spans more than 40 years. Jack Kemler began his career in 1983 as a patrol officer working for the Trenton Police Department. His assignments included stints as a K-9 handler, narcotics officer, and detective in the Criminal Investigation Bureau. In 1997, he was promoted to Sergeant and assigned to the Criminal Investigation Bureau, where he supervised the Violent Crimes Squad.

Jack Kemler received numerous awards and accommodations throughout his career but is most proud of being selected by his peers for the Trenton Kiwanis' Officer of The Year in 1990 for his professionalism and valor. In December 2002, he was appointed Chief Sheriff Officer. Kemler has also held the titles of Chief Warrant Officer and Undersheriff and has overseen all aspects of the Sheriff’s Office. He became Mercer County Sheriff in 2010 and has been elected and successively re-elected by the people of Mercer County.

Under Jack Kemler's highly respected leadership, the Mercer County Sheriff's Office continues its long-standing history of working closely with Federal, State, and local law enforcement to keep our communities safe. The Sheriff maintains his charge to have warrants served on behalf of the courts and apprehend fugitives with swiftness and efficiency. Sheriff Kemler maintains a strong working relationship with the Office of the State Attorney General, the NJ State Police, local police chiefs, the United States Marshal's Task Forces, and the Mercer County Prosecutor's Office. Sheriff Kemler and his staff oversee assignments to highly skilled specialty units throughout the County and assigns key Sheriff's Officers to the Homicide Task Force under the direct supervision of the Mercer County Prosecutor's Office. Additionally, Sheriff Kemler and his senior officers participate in various briefings and strategies that coordinate Federal, State, and local responses to criminal activity in the greater Trenton area. Lastly, under Sheriff Kemler's direction, the Mercer County Sheriff's Office has experienced overwhelming media and public support for the revival of "Mercer's Most Wanted" to apprehend fugitives who roam our streets.

Sheriff Jack Kemler is a proud public servant who works honorably and conscientiously, with a dedication to the County in which he serves. He advocates cooperative efforts to protect Mercer County residents with common-sense approaches to maintain public safety.