Wis. Stat. § 898.22: Voluntary return.

In every suit brought by a sheriff on such bond the defendants may plead a voluntary return of the prisoner to the jail from which the prisoner escaped, or the liberties thereof, or the recapture of such prisoner by the sheriff from whose custody the prisoner escaped before the commencement of such suit, and may give evidence thereof in mitigation of the damages or judgment claimed, but upon such answer of a voluntary return judgment shall be rendered against the defendant in the action for $25 for each day or part of day such defendant was outside of such liberties, together with the costs of the action; and such defendants shall be entitled to make such or any other defense to such suit which might be made by such sheriff to an action against the sheriff for such escape.