Caselaw prior to amendments to §§ 907.01-.03 may be found: here. These sections were amended by 2011 Wis Act 2 (eff. date 2/1/11), as follows:
907.01 Opinion testimony by lay witnesses. (intro.) If the witness is not testifying as an expert, the witness’s testimony in the form of opinions or inferences is limited to those opinions or inferences which are rationally all of the following:
(1) Rationally based on the perception of the witness and helpful.
(2) Helpful to a clear understanding of the witness’s testimony or the determination of a fact in issue.
Section 34. 907.01 (3) of the statutes is created to read:
907.01 (3) Not based on scientific, technical, or other specialized knowledge within the scope of a witness under s. 907.02 (1).
Section 34m. 907.02 of the statutes is renumbered 907.02 (1) and 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 testimony is based upon sufficient facts or data, the testimony is the product of reliable principles and methods, and the witness has applied the principles and methods reliably to the facts of the case.
Section 37. 907.02 (2) of the statutes is created to read:
907.02 (2) Notwithstanding sub. (1), the testimony of an expert witness may not be admitted if the expert witness is entitled to receive any compensation contingent on the outcome of any claim or case with respect to which the testimony is being offered.
Section 38. 907.03 of the statutes is amended to read:
907.03 Bases of opinion testimony by experts. The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to the expert at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence in order for the opinion or inference to be admitted. Facts or data that are otherwise inadmissible may not be disclosed to the jury by the proponent of the opinion or inference unless the court determines that their probative value in assisting the jury to evaluate the expert’s opinion or inference substantially outweighs their prejudicial effect.