Utah Code § 77-7-4: Magistrate may orally order arrest.

A magistrate may orally require a peace officer to arrest anyone committing or attempting to commit a public offense in the presence of the magistrate, and, in the case of an emergency, when probable cause exists, a magistrate may orally authorize a peace officer to arrest a person for a public offense, and thereafter, as soon as practical, an information shall be filed against the person arrested.