Wis. Stat. § 885.10
Upon satisfactory proof of the financial inability of the respondent or defendant to procure the attendance of witnesses for his or her defense, the judge or supplemental court commissioner, in any paternity proceeding or criminal action or proceeding, or in any other case in which the respondent or defendant is represented by the state public defender or by assigned counsel under s. 977.08 , to be tried or heard before him or her, may direct the witnesses to be subpoenaed as he or she determines is proper and necessary, upon the respondent's or defendant's oath or affidavit or that of the respondent's or defendant's attorney. Witnesses so subpoenaed shall be paid their fees in the manner that witnesses for the state therein are paid. Determination of indigency under s. 977.07 is proof of the respondent's or defendant's financial inability to procure the attendance of witnesses for his or her defense.
Wis. Stat. § 885.10