Wisconsin Expert Witness Rules: What Litigators Need to Know

Wisconsin’s expert witness framework is largely governed by its civil procedure and evidentiary rules, which emphasize thorough disclosure, fair notice, and methodological reliability. While the state does not follow the federal rules verbatim, it maintains a robust gatekeeping standard and requires expert compliance through structured discovery obligations. Especially in medical malpractice and product liability litigation, the admissibility and timing of expert testimony can determine whether a case advances or is dismissed.

Designation Requirements

Wisconsin does not require a formal “designation” of experts through a separate court motion. Instead, expert identification occurs through interrogatory responses and compliance with discovery deadlines, primarily under Wis. Stat. § 804.01 and § 804.10.

Each party is required to disclose:

• The name and address of the expert
• The subject matter of testimony
• A summary of the facts and opinions
• The basis of those opinions
• Any materials relied upon

Although not as detailed as Federal Rule 26, the required disclosure must provide enough information to permit meaningful cross-examination and rebuttal. Failure to make a timely or adequate disclosure may result in exclusion of the expert’s testimony under Wis. Stat. § 804.12, the state’s rule governing discovery sanctions.

Expert Disclosure Process

The primary mechanism for expert disclosure in Wisconsin litigation is through written interrogatories and court-ordered deadlines. Under Wis. Stat. § 804.01(2)(d), parties may serve interrogatories specifically requesting expert information, and the responding party must detail the expert’s:

• Qualifications and field of expertise
• Opinions to be expressed
• Basis for those opinions
• Materials considered
• Prior testimony, if requested

Expert reports are not mandatory unless required by a case scheduling order or stipulated by the parties. However, where experts are expected to offer complex or technical opinions, Wisconsin courts may order production of written reports to promote efficiency and reduce trial surprise.

Required Declarations

While Wisconsin does not require expert declarations at the disclosure stage, they are essential for summary judgment proceedings under Wis. Stat. § 802.08(3). If a party relies on expert opinion to create or oppose a genuine issue of material fact, the opinion must be submitted in the form of a sworn affidavit or declaration.

These affidavits must:

• Be based on personal knowledge
• Present admissible facts
• Demonstrate that the affiant is competent to testify
• Detail the expert’s qualifications and basis for opinions

In medical malpractice cases, expert affidavits are critical. Wisconsin law requires plaintiffs to support their claims with expert testimony, unless the alleged negligence is so obvious that it falls within the common knowledge of laypersons.

Fees and Compensation

Wisconsin imposes specific compensation rules for expert witnesses. Under Wis. Stat. § 814.67(1)(b), compensation for expert testimony in court is limited to:

• $100 per day for in-court testimony, unless a higher rate is authorized by the court

However, when it comes to depositions, experts may charge reasonable market rates, and the party requesting the deposition must pay the expert’s fee under Wis. Stat. § 804.01(2)(d). If disputes arise regarding fees, the court may intervene to assess reasonableness, especially where the expert is court-appointed or essential to the proceedings.

Discovery Scope and Limitations

Wisconsin allows broad expert discovery but imposes limits to prevent abuse. Discovery is permitted regarding:

• Testifying experts: Full scope of opinions, facts relied on, and qualifications
• Consulting experts: Discovery allowed only upon a showing of exceptional circumstances

Under Wis. Stat. § 804.01(2)(d), parties may request:

• Expert resumes and CVs
• The identity of materials reviewed
• Compensation agreements
• The identity of prior cases in which the expert has testified

Importantly, draft reports and attorney-expert communications are not explicitly protected under Wisconsin’s procedural rules. However, courts often extend work-product protection to such materials, unless the opposing party can show substantial need or undue hardship.

Admissibility Standards

Wisconsin follows a Daubert-based standard for the admissibility of expert testimony. In 2011, the state legislature amended Wis. Stat. § 907.02 to adopt language nearly identical to Federal Rule of Evidence 702. As a result, expert testimony is only admissible if:

1. The expert is qualified by knowledge, skill, experience, training, or education
2. The testimony is based on sufficient facts or data
3. The testimony is the product of reliable principles and methods
4. The expert has applied the principles and methods reliably to the case

Wisconsin courts act as gatekeepers to ensure expert testimony meets these reliability standards. Judges may conduct Daubert hearings prior to trial to evaluate whether an expert’s opinion is grounded in scientifically valid reasoning.

This reliability test applies broadly, including to medical, scientific, technical, and financial experts.

Key Deadlines & Strategy Notes

Wisconsin does not mandate statewide expert disclosure deadlines. Instead, deadlines are set in case-specific scheduling orders, often entered under Wis. Stat. § 802.10(3). Typical timelines include:

• Expert disclosure: 90–120 days before trial
• Rebuttal experts: 30–60 days after initial disclosure
• Daubert motions or motions in limine: Must comply with deadlines in the scheduling order, often 30–45 days before trial
• Summary judgment: Expert affidavits must accompany briefs under § 802.08

In medical malpractice litigation, early expert retention is essential due to the strict requirement that plaintiffs produce expert testimony to prove breach and causation. Failure to do so routinely results in dismissal.

State-Specific Statutes & Local Rules

• Wis. Stat. § 804.01(2)(d): Expert discovery procedures
• Wis. Stat. § 907.02: Standard for admissibility of expert testimony (Daubert standard)
• Wis. Stat. § 802.08: Summary judgment requirements, including expert affidavits
• Wis. Stat. § 814.67(1)(b): Compensation for expert witnesses
• Wis. Stat. § 802.10(3): Scheduling conferences and orders controlling expert timelines

Local courts in Milwaukee, Dane, and Waukesha counties often issue tailored scheduling orders that adjust disclosure obligations or require specific formats for expert reports or affidavits. Practitioners should always consult the relevant scheduling order and judge-specific protocols.