Wis. Stat. § 906.11: Mode and order of interrogation and presentation.

(1) Control by judge. The judge shall exercise reasonable control over the mode and order of interrogating witnesses and presenting evidence so as to do all of the following:

(a) Make the interrogation and presentation effective for the ascertainment of the truth.

(b) Avoid needless consumption of time.

(c) Protect witnesses from harassment or undue embarrassment.

(2) Scope of cross-examination. A witness may be cross-examined on any matter relevant to any issue in the case, including credibility. In the interests of justice, the judge may limit cross-examination with respect to matters not testified to on direct examination.

(3) Leading questions. Leading questions should not be used on the direct examination of a witness except as may be necessary to develop the witness’s testimony. Ordinarily leading questions should be permitted on cross-examination. In civil cases, a party is entitled to call an adverse party or witness identified with the adverse party and interrogate by leading questions.