A member of the common council of a town incorporated under the provisions of this article shall not be personally liable in damages or otherwise for an unlawful act of an officer or employee of the town, unless the act is committed by the authority of the member, or he has notice or knowledge thereof, or unless the act is committed under circumstances which would cause, or would have caused, a reasonable or prudent person to have knowledge of the act.
A.R.S. § 9-255