Expert Witnesses in Wyoming
Under Wyoming Rule of Evidence 702 (the version effective August 1, 2019), a witness qualifies as an expert if they possess knowledge, skill, experience, training, or education in a relevant field. These qualifications aren't mutually exclusive — any one or a combination can suffice.
Once qualified, the expert may testify in the form of an opinion or otherwise, provided four conditions are met: their specialized knowledge will help the trier of fact understand the evidence or determine a fact in issue; the testimony is based on sufficient facts or data; the testimony is the product of reliable principles and methods; and the expert has reliably applied those principles and methods to the facts of the case.
Rules Governing Disclosure
The written report must be prepared and signed by the expert witness (or, alternatively, a disclosure signed by counsel for the party). It must contain six mandatory elements:
First, a complete statement of all opinions the witness will express, together with the basis and reasons for each. Second, the facts or data the witness considered in forming those opinions. Third, any exhibits that will be used to summarize or support the opinions. Fourth, the witness's qualifications, including a list of all publications authored in the previous ten years. Fifth, a list of all other cases in which the witness testified as an expert at trial or by deposition during the previous four years. Sixth, a statement of the compensation to be paid for the study and testimony in the case.
The word "complete" in the first element is doing heavy lifting — it means the report must fully disclose the expert's opinion landscape, not just the highlights. Any opinion not included in the report risks exclusion under Rule 37(c)(1).
The default deadlines, absent a court order or stipulation, are: at least 90 days before the trial date or the date the case must be ready for trial for affirmative experts, and within 30 days after the other party's disclosure for rebuttal experts — those whose evidence is intended solely to contradict or rebut evidence on the same subject matter identified by another party under (B) or (C).
Admissibility Standards
The Wyoming Supreme Court adopted the federal Daubert model, imposing gatekeeping responsibilities on trial courts deciding whether scientific or technical expert testimony is admissible. Critically, however, the court did not "abandon our own precedent regarding the admissibility of expert testimony." Wyoming's adoption of Daubert was additive — it layered the Daubert framework onto existing Wyoming precedent rather than replacing it.
Attorney–Expert Communication Protection
Communications between a party's attorney and any expert witness required to provide a written report under Rule 26(a)(2)(B) are protected as trial-preparation material. The protection applies "regardless of the form of the communications" — so it covers emails, phone calls, texts, in-person meetings, marked-up drafts, shared documents, and anything else.
The protection does not extend to communications that fall into any of three categories.
The first exception covers communications relating to compensation for the expert's study or testimony. This is discoverable because the jury is entitled to know what financial incentive the expert has, and the expert report itself must include a compensation statement under Rule 26(a)(2)(B)(vi). The exception ensures that side arrangements, contingency structures, or escalating fee discussions that might not appear in the formal compensation statement are still reachable.
The second exception covers communications that identify facts or data the party's attorney provided and that the expert considered in forming the opinions to be expressed. This targets attorney-fed inputs. If the lawyer handed the expert a curated subset of documents, selected data points, or specific factual narratives — and the expert actually considered those in forming opinions — the opposing party can discover what was provided. The operative language is "provided and that the expert considered," so facts or data the attorney sent but the expert disregarded would arguably remain protected.
The third exception covers communications that identify assumptions the party's attorney provided and that the expert relied on in forming the opinions to be expressed. This is narrower than the facts-or-data exception in one respect: it uses "relied on" rather than "considered." An assumption the attorney floated but the expert ultimately rejected would not fall within this exception. But when the attorney tells the expert "assume liability has been established" or "assume the contract was breached as of this date" and the expert builds an opinion on that foundation, the opposing party can discover that the assumption came from counsel rather than from the expert's independent analysis.
Compensation
Unless manifest injustice would result, the court must require the party seeking discovery to pay the expert a reasonable fee for time spent responding to discovery under Rule 26(b)(4)(A). This covers depositions of retained testifying experts. The rule is mandatory ("must require"), not discretionary — the only escape valve is manifest injustice. The fee must be "reasonable," which the court determines.
Limits on Number of Expert Witnesses
Wyoming does not impose a fixed numerical cap on expert witnesses through its rules of procedure or evidence. But the court may take appropriate action on "avoiding unnecessary proof and cumulative evidence, and limiting the use of testimony under Wyoming Rule of Evidence 702" at any pretrial conference.
Out-of-State Expert Qualification
Wyoming places no formal bar on out-of-state experts. The qualification inquiry under W.R.E. 702 is expertise-based, not geography-based. The practical challenges for out-of-state experts are substantive (demonstrating familiarity with Wyoming's standard of care in medical cases), methodological (surviving Daubert scrutiny), and logistical (deposition mechanics, subpoena reach, and trial attendance). None of these are unique barriers to out-of-state experts — they're the same hurdles every expert faces, just with an added layer of complexity when the expert is practicing across state lines.
