Arrest or custodial arrest is the process in which the police take physical possession or custody of a person whom they have probable cause to believe committed a criminal offense. Arrest is distinguishable from other circumstances in which the police stop, detain, or otherwise interact with persons because it is generally the point at which a person is not free to leave or walk away from the police. Arrest is also the point at which some Constitutional rights and protections are provided to the accused. A person who is placed in handcuffs or otherwise physically restrained is clearly under arrest—but in some circumstances a person may be under arrest due to threats or intimidation from the police.

In New Hampshire, an arrest or custodial arrest occurs when law enforcement takes a person into physical custody based on probable cause that the individual has committed a criminal offense. This is a more severe action than a mere stop or detention, as it typically means the individual is not free to leave the presence of the police. The moment of arrest triggers certain Constitutional rights for the accused, such as the right to remain silent and the right to an attorney. While physical restraint, such as handcuffs, is a clear indication of arrest, a person may also be considered under arrest if they are subjected to coercion or intimidation by police that effectively restricts their freedom to depart. New Hampshire law enforcement must adhere to both state statutes and federal law, including the Fourth Amendment of the U.S. Constitution, which protects individuals against unreasonable searches and seizures.