What is required for a law enforcement officer to legally stop a motor vehicle?

The requirement for a law enforcement officer to legally stop a motor vehicle is reasonable articulable suspicion. This standard is based on specific and articulable facts that suggest a crime may be occurring, allowing officers to engage in a brief investigatory stop. Unlike probable cause, which is a higher standard that requires more concrete evidence to believe a crime has already been committed, reasonable articulable suspicion allows for a stop based on a lower threshold of evidence.

A warrant is not necessary for a traffic stop because law enforcement can stop a vehicle if they have sufficient suspicion of wrongdoing in the moment. Proof beyond a reasonable doubt is the highest standard of proof used in criminal trials and is not applicable in the context of making a traffic stop. Thus, reasonable articulable suspicion is the appropriate standard that law enforcement officers must have to initiate a stop of a motor vehicle.