What constitutes an arrest in legal terms?

In legal terms, an arrest is defined as taking a suspect into custody based on probable cause, which means that law enforcement has sufficient reason to believe that a person has committed a crime. This action involves the physical restraint of the individual and a clear intention by the police or law enforcement officers to exercise authority over that person.

This definition is significant because it emphasizes the requirement of probable cause, which serves as a legal standard that protects individuals from arbitrary detainment. The act of arrest typically requires specific procedures to be followed, such as informing the suspect of the charges against them and their rights.

The other options do not meet the legal criteria for an arrest. A formal warning does not involve taking someone into custody; a request for a suspect to stay in a location does not imply that they have been arrested or that they are not free to leave; and merely observing a suspect's actions does not constitute an arrest unless it leads to an action taken based on evidence gathered. Thus, taking someone into custody based on probable cause accurately describes the arrest process in legal terms.