What must be established to stop a vehicle legally?

To legally stop a vehicle, there must be an initial observation of the vehicle in operation that provides enough evidence for a stop. This requirement stems from the concept of reasonable suspicion, which is necessary for law enforcement to engage a vehicle. If a police officer observes a violation of traffic laws or suspicious behavior while the vehicle is in motion, this creates a legal basis for the stop.

The other options, while they may play a role in law enforcement practices, do not provide the foundational justification required for a legal stop. Personal suspicion alone, without observable behavior or violations, is insufficient for a legal stop. Similarly, information from an informant can be useful, but it must be corroborated by additional evidence to establish reasonable suspicion. A reported crime in progress can certainly justify police action, but the officer must also have an observable reason to stop that specific vehicle in relation to the crime. Thus, the requirement of an initial observation of the vehicle in operation is critical for establishing the legality of the stop.