Wis. Stat. § 345.421: Discovery.

Neither party is entitled to pretrial discovery except that if the defendant moves within 10 days after the alleged violation and shows cause therefor, the court may order that the defendant be allowed to inspect and test under s. 804.09 and under such conditions as the court prescribes, any devices used by the plaintiff to determine whether a violation has been committed, including without limitation, devices used to determine presence of alcohol in breath or body fluid or to measure speed, and may inspect under s. 804.09 the reports of experts relating to those devices.