Iowa Code § 321E.17

Proof of imposition of a penalty for a violation of section 321.256, 321.454, 321.456, 321.457, 321.463, 321.471, 321.474, or 321E.16 or any combination of penalties for violation of those sections with respect to the operation of one or more vehicles by any one permit holder, whether operated personally or through agents, servants, or employees of the permit holder, shall constitute prima facie evidence that the permit holder has willfully operated or caused to be operated a vehicle or vehicles in violation of this chapter.