Admissibility of expert witness testimony, the official text

2025 - 2026 LEGISLATURE
LRB-4653/1
SWB:cjs

2025 SENATE BILL 459
October 2, 2025 - Introduced by Senators Wanggaard, Feyen, Marklein and Wimberger, cosponsored by Representatives B. Jacobson, Kreibich, Moses, Murphy, Mursau, O'Connor, Penterman, Piwowarczyk, Tittl, VanderMeer, Wittke and Duchow. Referred to Committee on Judiciary and Public Safety.
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An Act to amend 907.02 (1) of the statutes; relating to: admissibility of expert witness testimony.

Analysis by the Legislative Reference Bureau
This bill updates the current statutory rule of evidence relating to testimony by experts to conform with recent changes made to Federal Rule of Evidence (FRE) 702 intended to clarify the court’s gatekeeping role with respect to expert testimony. Current law parallels FRE 702 prior to its amendment, allowing the testimony of an expert witness if the witness’s scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact at issue in the case, but limiting the testimony of an expert witness to testimony that is based on sufficient facts or data, that is the product of reliable principles and methods, and that is based on the witness applying those principles and methods reliably to the facts of the case. Similar to the changes made to FRE 702, the bill confirms that the proponent of the testimony is required to demonstrate to the court that it is more likely than not that the witness’s testimony is based upon sufficient facts or data, that it is the product of reliable principles and methods, and, finally, that the witness’s opinion reflects a reliable application of those principles and methods to the facts of the case.

The people of the state of Wisconsin, represented in senate and assembly, do enact as follows:

Section 1. 907.02 (1) of the statutes is amended to read:
907.02 (1) If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if the proponent demonstrates to the court that it is more likely than not that the testimony is based upon sufficient facts or data, the testimony is the product of reliable principles and methods, and the witness has applied witness’s opinion reflects a reliable application of the principles and methods reliably to the facts of the case.
Section 2. Initial applicability.
(1) This act first applies to actions or special proceedings that are commenced on the effective date of this subsection.
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