Wisconsin Statutes & Annotations
Chapter 907 - Evidence — opinions and expert testimony.
907.01 - Opinion testimony by lay witnesses.

907.01 Opinion testimony by lay witnesses. 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 all of the following:
(1) Rationally based on the perception of the witness.
(2) Helpful to a clear understanding of the witness's testimony or the determination of a fact in issue.
(3) Not based on scientific, technical, or other specialized knowledge within the scope of a witness under s. 907.02 (1).
History: Sup. Ct. Order, 59 Wis. 2d R1, R205 (1973); 1991 a. 32; 2011 a. 2.
When a victim admitted injecting heroin about 72 hours before testifying, the trial court properly denied the defendant's request that the witness display his arm in the presence of the jury in an attempt to prove that the injection was more recent. Edwards v. State, 49 Wis. 2d 105, 181 N.W.2d 383 (1970).
An attorney, not qualified as an expert, could testify regarding negotiations in which the attorney was an actor, including expressing opinions about the transaction, but could not testify as to what a reasonably competent attorney would or should do in similar circumstances. Hennig v. Ahearn, 230 Wis. 2d 149, 601 N.W.2d 14 (Ct. App. 1999), 98-2319.
Using Lay Opinion Evidence at Trial. Coaty. Wis. Law. May 2009.

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