Under what circumstance is an officer not allowed to make an arrest without a warrant?

An officer is not allowed to make an arrest without a warrant in scenarios where the offense was not observed by them directly, but instead is reported by a citizen. In this specific case, an officer cannot arrest someone based solely on a traffic violation, such as running a red light, that was witnessed by a citizen and not by the officer themselves. This is because the officer must have personal knowledge or observation of the offense to justify making an arrest without a warrant.

In contrast, if an offense is committed in the officer's presence, the law allows them to act immediately. Similarly, if a credible citizen reports witnessing a felony, the officer can use that information in conjunction with their own observations to proceed with an arrest. Observing suspicious activities also provides grounds for an officer to intervene if they have witnessed those activities first-hand.