Which of the following is NOT a circumstance where a warrant is needed by police?

In considering when a warrant is not required for police to act, it is important to understand the context behind various scenarios.

When a suspect is fleeing, police are often granted the authority to pursue and apprehend that individual without needing a warrant. This is based on the principle that an immediate response is necessary to prevent harm or avoid the suspect escaping. The concept of "exigent circumstances" comes into play here—law enforcement can act quickly to avoid losing the opportunity to capture a suspect who is actively evading arrest.

On the other hand, obtaining a warrant is typically required in situations where police act based solely on a tip-off or information received without immediate evidence or circumstances that necessitate swift action. A similar principle applies when officers find something in plain view; this is considered an exception to the warrant requirement because the evidence is observable without intrusion. Lastly, if a suspect has already been legally arrested, any evidence gathered in the course of that arrest may be lawfully seized without additional warrants under the search incident to a lawful arrest doctrine.

Therefore, the correct answer reflects an understanding that police can act without warrants in specific urgent circumstances, which include a suspect fleeing.