NH Rev Stat § 105:13 (2021)
2021 New Hampshire Revised Statutes|Title VII - Sheriffs, Constables, and Police Officers|Title 105 - Police Officers and Watchmen|Section 105:13 - Extended Authority.

    105:13 Extended Authority. –||I. The authority of any duly authorized police officer, constable or watchman of any town or city shall extend to any other city or town in the state, provided that the chief law enforcement officer of the requesting town or city has executed with the chief law enforcement officer of the responding town or city a written agreement which sets forth the terms and conditions under which such assistance may be requested or rendered. The executed agreement shall constitute authorization for every request for assistance, and for any assistance rendered in accordance with the terms and conditions of the written agreement, regardless of whether the responding police officer, constable, or watchman is named in the agreement. In an emergency situation, the ranking on-duty law enforcement official of a town or city is authorized to make an oral request for assistance to the ranking on-duty law enforcement official in the responding town, subject to the terms and conditions of such written agreement, and the authority of the responding police officer, constable, or watchman shall extend to the requesting town. The written agreement shall remain in full force and effect until terminated by the mutual consent of the chief law enforcement officers of each town or city, or until 10 days after the chief law enforcement officer of one town or city has received notification from the chief law enforcement officer of the other town or city of his or her intention to terminate.||II. Where no written agreement exists or no officer is available, any duly authorized police officer, constable, or watchman shall have temporary police authority in another jurisdiction in the state, when requested by a law enforcement officer from such jurisdiction in the state to render assistance to such officer under such officer's direction in an emergency for the purposes of making an arrest or effecting custody of a detainee, conducting a search, quelling a disturbance, providing traffic or crowd control, holding an arrested person in need of medical treatment in temporary custody until medically cleared to enter a state or county correctional facility or municipal jail, or securing a crime scene, until relieved by the requesting officer or otherwise directed by the ranking on-duty officer of the requesting jurisdiction.||III. Where no written agreement exists or no officer is available, any duly authorized police officer, constable, or watchman from a nearby town or city may exercise temporary police authority as necessary to respond to a crime in progress, traffic accident, natural or human-caused disaster, disturbance in progress, or other emergency, if requested by a public safety dispatch center authorized to dispatch for the jurisdiction where the event is occurring, because there is no local officer or state trooper available for immediate response and in the judgment of the dispatch center the public safety requires an immediate response. Such officer's authority shall terminate when relieved by an officer with authority in the jurisdiction receiving the assistance, unless the officer with authority requests assistance pursuant to paragraph II.||IV. When providing assistance under this section the officer shall remain an employee of his or her respective department.|||Source. 1971, 390:2. 1981, 297:1. 2008, 260:1, eff. Aug. 25, 2008. 2017, 139:1, eff. June 16, 2017.|