A peace officer, without a warrant, may arrest a person if the officer has probable cause to believe: 1. A felony has been committed.The authority to arrest depends on the existence of a crime or arrest warrant; without a crime or arrest warrant, there can be no arrest. Because of this "Failure to Appear," the judge may authorize police to make an arrest of the individual listed on the warrant. "Probable cause" is the standard required for a law enforcement officer to make an arrest as it relates to DUI or other criminal charges. Police officers do not need a warrant to perform a search in connection with an arrest. Arizona statutes refer to no-knock warrants as "unannounced entry" warrants. They are the same thing. The police may make an investigative stop, without a warrant, when they have a reasonable suspicion that criminal activity is afoot. Read Section 13-3898 - Arrest without warrant; magistrate; complaint, Ariz. Rev. Stat.