Wis. Stat. § 968.26

If a person complains to a judge that he or she has reason to believe that a crime has been committed within his or her jurisdiction, the judge shall examine the complainant under oath and any witnesses produced by him or her and may, and at the request of the district attorney shall, subpoena and examine other witnesses to ascertain whether a crime has been committed and by whom committed. The extent to which the judge may proceed in the examination is within the judge's discretion. The examination may be adjourned and may be secret. Any witness examined under this section may have counsel present at the examination but the counsel shall not be allowed to examine his or her client, cross-examine other witnesses or argue before the judge. If it appears probable from the testimony given that a crime has been committed and who committed it, the complaint may be reduced to writing and signed and verified; and thereupon a warrant shall issue for the arrest of the accused. Subject to s. 971.23 , if the proceeding is secret, the record of the proceeding and the testimony taken shall not be open to inspection by anyone except the district attorney unless it is used by the prosecution at the preliminary hearing or the trial of the accused and then only to the extent that it is so used. A court, on the motion of a district attorney, may compel a person to testify or produce evidence under s. 972.08 (1) . The person is immune from prosecution as provided in s. 972.08 (1) , subject to the restrictions under s. 972.085 .