1. The officer shall, without unnecessary delay, take the person arrested pursuant to section 804.11 before the nearest or most accessible magistrate to the place where the arrest occurred.
2. At the appearance before the magistrate, the law enforcement officer shall make a showing to the magistrate, by sworn affidavit, that probable cause exists to believe that a person is a necessary and material witness to a felony and that such person might be unavailable for service of a subpoena. The magistrate may order the person released pursuant to section 811.2.
Proceedings before magistrate, see