Expert Witnesses in Oklahoma
In Oklahoma, expert witnesses are individuals qualified by knowledge, skill, experience, training, or education to provide specialized opinions that assist the court in understanding evidence or determining facts in issue.
Governing Law
Primary statutory authority:
12 Okla. Stat. § 3226 — governs expert discovery/disclosure scope and timing.
12 Okla. Stat. § 2702 — expert admissibility standards (similar to federal Daubert).
12 Okla. Stat. § 2705 — permits expert opinion testimony without prior disclosure of underlying data unless the court orders otherwise.
Disclosure Requirements
Name and address of each expert expected to testify.
Subject matter on which the expert will testify.
Substance of facts and opinions expected to be offered.
A summary of the grounds/basis for each opinion the expert intends to offer.
Qualifications (education, training, experience), including a list of all publications authored by the expert witness within the preceding ten (10) years
Data or information considered in forming opinions.
the compensation to be paid to the expert witness for the testimony and preparation for the testimony.
A listing of any other cases in which the expert witness has testified as an expert at trial or by deposition within the preceding four (4) years.
Timing
Oklahoma doesn’t set fixed statewide deadlines in the statute. Instead:
Scheduling orders from the trial court typically set deadlines.
Common practice in many cases:
o Plaintiff expert disclosures ~90 days before trial.
o Defendant expert disclosures ~60 days before trial.
o Rebuttal expert disclosures later if needed.
These timelines are guidelines and may be modified by the court in complex cases or by agreement of the parties.
Expert Disclosure in Oklahoma Criminal Cases
Unlike civil cases, Oklahoma does not require broad, report-style expert disclosures in criminal prosecutions. Expert discovery is governed by statute and constitutional principles rather than by a detailed rule like Federal Rule 16.
Admissibility Standards
In 2025, the Oklahoma Legislature amended 12 O.S. § 2702, which governs when expert testimony is admissible in Oklahoma courts. The amended statute now requires that a party offering expert testimony must persuade the court that it is “more likely than not” that all admissibility criteria are met, including:
The expert’s specialized knowledge will help the fact-finder understand or determine a fact;
The testimony is based on sufficient facts or data;
The testimony is the product of reliable principles and methods; and
The expert’s opinion reliably applies those principles and methods to the facts of the case.
This mirrors amendments made to Federal Rule of Evidence 702 and shifts the focus toward a clearer preponderance-of-the-evidence burden on admissibility. Rather than assuming admissibility unless excluded, the offering party must affirmatively show reliability and relevance to a degree of likelihood.
Before 2025, Oklahoma followed general Daubert-style requirements without clear statutory language about the burden of proof.
Communication Between Attorneys and Experts
Oklahoma law generally protects attorney-expert communications as work product, except for communications that:
(1) concern the expert’s compensation for study or testimony;
(2) identify facts or data provided by the attorney that the expert considered in forming the opinions to be offered; or
(3) identify assumptions supplied by the attorney that the expert relied upon in forming those opinions.
Expert Witness Depositions
Expert depositions in Oklahoma civil cases are governed by:
12 O.S. § 3226 – Discovery of experts
12 O.S. § 3230 – Depositions upon oral examination
Oklahoma’s approach is more flexible and court-controlled than the federal system.
A party may depose an expert who is expected to testify at trial once:
The expert has been identified, and
The expert’s opinions and bases have been disclosed (by interrogatory response, summary disclosure, or court-ordered report).
No statutory requirement for a formal written expert report exists in Oklahoma. However, many judges require a summary of opinions and grounds and a report-style disclosure by scheduling order.
Limits on the Number of Expert Witnesses
Oklahoma does not impose a statutory limit on the number of expert witnesses a party may call. However, courts have discretion to limit expert testimony to prevent cumulative or redundant evidence, ensuring efficiency and clarity during trials.
Out-of-State Expert Qualification
Out-of-state experts are allowed to testify in Oklahoma courts. Oklahoma law does not require an expert witness to live in Oklahoma or be licensed in the state simply to testify. An expert is qualified based on knowledge, skill, experience, training, or education, not location. Out-of-state experts are subject to the same disclosure, discovery, and admissibility rules as in-state experts.
Rebuttal Experts
In Oklahoma, the rebuttal expert must be identified once the need for rebuttal becomes clear. Oklahoma statutes do not set fixed deadlines. Timing is usually controlled by scheduling orders, pretrial conference rulings and court discretion.
Compensation
In Oklahoma, expert witnesses are compensated pursuant to private retention agreements, typically on an hourly or flat-fee basis.
In Jolley v. McClain, the Oklahoma Supreme Court held that expert witness income from prior cases is not discoverable through a subpoena duces tecum under the Oklahoma Discovery Code. This decision reaffirmed limits on expert discovery.
Sanctions for Failure to Disclose
Exclusion of Evidence or Expert Testimony
Continuance or Reopening Discovery
Limitation of Testimony
Cost-Shifting and Attorney’s Fees
Compelled Disclosure
