What determines the legality of an arrest made without a warrant?

The legality of an arrest made without a warrant primarily hinges on the presence of an offense. When an officer makes an arrest without a warrant, they must have probable cause that a crime has been, is being, or will be committed. This means the officer must have sufficient evidence or reasonable grounds to believe that a specific criminal act occurred. If this standard is not met, the arrest could be deemed unlawful, regardless of other factors like location, witness availability, or warrant status.

While the location of the arrest can play a role in permissible actions by law enforcement, it does not by itself determine the legality of the arrest without a warrant. Similarly, while witnesses might provide corroborative evidence of an offense, their availability does not independently establish legal grounds for an arrest. Warrant status also has its relevance, but it is the existence of an offense, established through probable cause, that is the primary criterion for ensuring the legality of a warrantless arrest.