Wyoming Expert Witness Rules: What Litigators Need to Know

Expert witnesses play a vital role in Wyoming civil litigation, especially in cases involving medical malpractice, oil and gas litigation, environmental damage, product liability, and complex commercial disputes. Wyoming’s procedural rules governing expert disclosure, discovery, and admissibility are based on the Wyoming Rules of Civil Procedure and Wyoming Rules of Evidence, both of which mirror federal standards. Expert evidence is subject to Daubert-style admissibility scrutiny, and compliance with disclosure requirements is essential to avoid exclusion.

Designation Requirements

Wyoming does not require expert witnesses to be designated by formal motion. Instead, parties must disclose their experts and their opinions in accordance with Rule 26(a)(2) of the Wyoming Rules of Civil Procedure.

When a party intends to call an expert at trial, they must provide:

• The expert’s name, contact information, and qualifications
• The subject matter on which the expert will testify
• A complete statement of all opinions the expert will express
• The basis and reasons for each opinion
• Any exhibits the expert intends to use to support the opinions
• A list of the expert’s publications from the past 10 years
• A list of all other cases in which the expert has testified within the past 4 years
• The expert’s compensation for study and testimony

These disclosures must be made at least 90 days before trial (or as set by a scheduling order). Failing to properly or timely disclose an expert can result in preclusion under Rule 37(c)(1).

Expert Disclosure Process

Wyoming requires detailed disclosures for any retained or specially employed experts expected to testify. Under Rule 26(a)(2)(B), the party must provide a written report prepared and signed by the expert, unless the court orders otherwise.

The report must include:

• A complete statement of opinions
• The basis and reasoning for each opinion
• The facts or data considered in forming the opinions
• All exhibits used to summarize or support the opinions
• The expert’s qualifications, including a list of publications
• A list of prior testimony within the past 4 years
• The expert’s compensation terms

Disclosure deadlines are usually set in the court’s scheduling order, and rebuttal expert disclosures are due 30 days after the initial disclosures, unless otherwise ordered.

Required Declarations

While declarations are not required during the disclosure phase, they are necessary for summary judgment practice. Under Wyo. R. Civ. P. 56(c)(4), expert affidavits or declarations must:

• Be based on personal knowledge
• Set forth facts that would be admissible at trial
• Show that the affiant is competent to testify

In cases involving medical negligence, engineering disputes, or scientific causation, courts expect a party opposing summary judgment to submit a qualified expert affidavit supporting key claims. Without such expert support, summary judgment is often granted for the defense.

Fees and Compensation

There are no statutory limits on expert compensation in Wyoming. Experts charge based on private contracts with retaining attorneys. However, when an expert is deposed by the opposing party, Rule 26(b)(4)(E) requires the deposing party to:

• Pay a reasonable fee for the time spent in deposition and preparation

If the parties disagree over what is “reasonable,” the court may intervene. Considerations include the expert’s credentials, time commitment, and customary rates in the field.

Discovery Scope and Limitations

Expert discovery in Wyoming is governed by Rule 26(b)(4), which allows:

• Interrogatories about the opinions of testifying experts
• Requests for documents or materials reviewed by the expert
• Depositions of experts after the Rule 26 disclosures are complete

Key discoverable items include:

• Expert opinions and the reasons behind them
• All facts, data, or assumptions the expert considered
• The expert’s CV, prior testimony, and compensation

Consulting experts—those retained but not expected to testify—are generally protected from discovery, unless the opposing party shows exceptional circumstances, such as the inability to obtain equivalent information elsewhere.

Draft expert reports and attorney-expert communications are typically protected under the work-product doctrine, though facts and data relied upon remain discoverable.

Admissibility Standards

Wyoming follows the Daubert standard, codified in Rule 702 of the Wyoming Rules of Evidence. Courts are tasked with acting as gatekeepers, ensuring that expert testimony is not only relevant but also reliable.

To be admissible under Rule 702, expert testimony must:

1. Be offered by a qualified expert
2. Be based on sufficient facts or data
3. Be the product of reliable principles and methods
4. Be reliably applied to the facts of the case

In Bunting v. Jamieson, 984 P.2d 467 (Wyo. 1999), the Wyoming Supreme Court expressly adopted Daubert as the standard for scientific expert testimony. Courts may hold Daubert hearings to evaluate reliability factors such as:

• Testability of the theory or technique
• Peer review and publication
• Error rates and control standards
• General acceptance in the relevant field

Experts must be prepared to explain and defend their methodology in pretrial hearings or risk exclusion.

Key Deadlines & Strategy Notes

Expert disclosure timelines are usually established by the court’s scheduling order. Common deadlines include:

• Initial expert disclosures: 90–120 days before trial
• Rebuttal expert disclosures: 30 days after initial disclosures
• Expert depositions: Before discovery cutoff
• Motions to exclude (Daubert challenges): Typically due before the final pretrial conference

Strategically, Wyoming attorneys should retain and prepare experts early, especially in technical, medical, or scientific cases. Comprehensive disclosures, supported by detailed expert reports, reduce the likelihood of exclusion and help streamline admissibility challenges.

State-Specific Statutes & Local Rules

• Wyo. R. Civ. P. 26(a)(2): Governs expert witness disclosures and reports
• Wyo. R. Civ. P. 26(b)(4): Allows discovery of testifying experts
• Wyo. R. Civ. P. 56(c)(4): Affidavit requirements for summary judgment
• Wyo. R. Evid. 702: Codifies Daubert standard
• Bunting v. Jamieson, 984 P.2d 467 (Wyo. 1999): Leading case adopting Daubert in Wyoming

Some courts—particularly in Laramie, Natrona, and Campbell Counties—may include standing orders or local scheduling protocols that govern expert disclosure formats, deadlines, and hearing procedures. Counsel should consult these court-specific resources to ensure full compliance.