Which out of the following is not a reason a peace officer can arrest without a warrant?

Arresting someone without a warrant requires certain specific conditions to be met as outlined by the law. A tip from an informant does not, on its own, provide the necessary grounds for an arrest without a warrant because it generally lacks sufficient corroborative evidence to establish probable cause. For peace officers to act on information provided by an informant, that information must usually be supported by some level of verification that indicates the informant is credible and their information is reliable.

On the other hand, options such as public intoxication and a suspect's own statements can directly lead to probable cause for arrest. Witnessing someone in a state of public intoxication clearly indicates that they are posing a risk to themselves or others, justifying immediate action by law enforcement. Similarly, a suspect's own admissions can establish direct evidence of a crime committed, validating an immediate arrest.

Suspicion of drug possession could also require more evidence for an arrest without a warrant, but it is generally stronger than mere informant tips that lack corroboration. Ultimately, the reliance on direct evidence or observable behavior triggers a lawful and immediate response by law enforcement, whereas a mere tip does not meet that threshold.