Oklahoma Expert Witness Rules: What Litigators Need to Know

Oklahoma courts apply structured rules governing expert witness disclosure, discovery, and admissibility, largely aligning with federal practice while retaining some state-specific nuances. Especially in civil litigation involving personal injury, medical malpractice, and complex torts, expert testimony plays a central role in establishing liability and damages. Litigators in Oklahoma must navigate detailed requirements related to expert disclosures, qualifications, and the admissibility of expert opinions to avoid preclusion or adverse rulings at trial.

Designation Requirements

There is no formal “designation” filing process for expert witnesses in Oklahoma. However, the rules require disclosure of testifying experts as part of pretrial discovery. Under Oklahoma Discovery Code, 12 O.S. § 3226(B)(4), a party must disclose the following about each expert expected to testify:

• The expert’s name and address
• The subject matter of the expected testimony
• The substance of the facts and opinions
• A summary of the grounds for each opinion

These disclosures are typically made in response to interrogatories or pursuant to a court-ordered scheduling order. Courts may preclude expert testimony if the required disclosures are untimely, incomplete, or not supplemented as discovery progresses, especially where failure to disclose causes prejudice.

Expert Disclosure Process

Under 12 O.S. § 3226, expert discovery is permitted through interrogatories, document requests, and depositions. Disclosures must include:

• A summary of opinions and the basis for those opinions
• Documents or data relied upon
• The expert’s qualifications, including a list of prior testimony
• Compensation arrangements

Although Oklahoma does not require a formal expert report in all cases, courts often encourage or order the production of reports in cases involving technical or scientific experts. In medical malpractice actions, additional affidavit requirements apply (discussed below).

Disclosure deadlines are typically set by a Scheduling Order issued at the outset of litigation, with staggered deadlines for plaintiff and defense experts, followed by rebuttal disclosures.

Required Declarations

Oklahoma does not mandate expert declarations as part of the routine disclosure process. However, they are often essential in summary judgment proceedings, especially when the expert’s opinion is the only evidence supporting or opposing an essential element of a claim.

Under 12 O.S. § 2056(E), affidavits submitted in support of or opposition to summary judgment must:

• Be made on personal knowledge
• Set forth facts admissible in evidence
• Demonstrate that the affiant is competent to testify on the matters stated

In medical liability actions, Oklahoma law previously required an affidavit of merit from a qualified expert under 63 O.S. § 1-1708.1E, but this requirement was declared unconstitutional in Wall v. Marouk, 302 P.3d 775 (Okla. 2013). Nevertheless, expert affidavits remain essential to withstand motions to dismiss or for summary judgment in cases involving professional standards of care.

Fees and Compensation

Expert witness compensation in Oklahoma is typically determined by private agreement. There is no statutory cap on fees. However, 12 O.S. § 3226(B)(4)(c)(2) requires that a party deposing an opposing expert must pay a reasonable fee for time spent in deposition.

Courts may intervene to determine reasonableness when there is a dispute. Factors considered include the expert’s customary rate, experience, subject matter complexity, and time involved.

Discovery Scope and Limitations

Discovery of expert opinions is governed by 12 O.S. § 3226(B)(4). The rules provide for the discovery of:

• The opinions the expert will offer
• The factual basis for those opinions
• Supporting documents, publications, or data
• The expert’s qualifications and prior testimony

Discovery of consulting experts—those retained but not expected to testify—is not permitted unless exceptional circumstances exist, such as the inability to obtain equivalent information by other means.

Communications between attorneys and testifying experts may be protected under the work-product doctrine, but facts, data, and assumptions relied upon by the expert are discoverable.

Admissibility Standards

Oklahoma follows a Daubert-style standard, codified in 12 O.S. § 2702 (Evidence Code Rule 702), and clarified through case law including Christian v. Gray, 65 P.3d 591 (Okla. 2003). Trial courts serve as gatekeepers and must evaluate both the relevance and reliability of expert testimony.

To be admissible under Rule 702, expert testimony must:

1. Be provided by a qualified expert
2. Assist the trier of fact to understand or determine a fact in issue
3. Be based on sufficient facts or data
4. Be the product of reliable principles and methods
5. Reflect the reliable application of those methods to the case facts

Courts often conduct Daubert hearings to assess admissibility. Inadequately supported opinions—particularly those based on speculation, untested methods, or anecdotal evidence—may be excluded.

Key Deadlines & Strategy Notes

Deadlines for expert disclosures are typically established in the case’s Scheduling Order, which varies by judge and jurisdiction. Common milestones include:

• Plaintiff’s expert disclosures: 90–120 days before trial
• Defendant’s expert disclosures: 30–60 days after plaintiff’s
• Rebuttal disclosures: Often required 30 days before trial
• Expert discovery cut-off: Usually 30–45 days before trial
• Motions to exclude experts: Must be filed before the pretrial conference

Strategically, early retention and vetting of experts is essential—particularly in medical negligence, products liability, and engineering cases. Courts are increasingly willing to hold Daubert hearings and exclude experts who cannot defend their methodology under scrutiny.

State-Specific Statutes & Local Rules

• 12 O.S. § 3226(B)(4): Governs expert disclosures and discovery scope
• 12 O.S. § 2702: Controls admissibility of expert testimony
• 12 O.S. § 2056(E): Affidavit requirements for summary judgment
• Christian v. Gray, 65 P.3d 591 (Okla. 2003): Oklahoma’s leading Daubert case
• Wall v. Marouk, 302 P.3d 775 (Okla. 2013): Invalidated affidavit of merit requirement in medical malpractice cases

Attorneys must also comply with local district court rules and judicial preferences in setting disclosure timelines, formats, and procedures for challenging experts. Regularly consulting with court staff and reviewing standing orders is essential to stay in compliance.