Missouri Expert Witness Rules: What Litigators Need to Know

Missouri maintains a distinct procedural framework for expert witnesses that blends traditional state practices with select federal-style reforms. While formal expert reports are not automatically required, courts have the authority to order them, and the admissibility threshold under Missouri’s updated Rule 490.065 mirrors key elements of the federal Daubert standard. In medical malpractice and complex litigation, expert testimony can determine the viability of a claim—making compliance with Missouri’s rules essential to case strategy.

Designation Requirements

Missouri does not require a motion-based designation process but mandates disclosure of expert witnesses through interrogatory responses and scheduling orders. Under Mo. Sup. Ct. R. 56.01(b)(4), parties must identify:

• The name and address of any expert expected to testify
• The general nature of the subject matter of testimony
• The substance of the facts and opinions
• A summary of the grounds for each opinion

Disclosure may also be compelled through formal discovery requests or by case management order. If a party fails to disclose an expert or withholds significant aspects of the testimony, the court may exclude the expert under Rule 61.01 for failure to comply with discovery obligations.

Expert Disclosure Process

Missouri civil courts do not automatically require expert reports, but trial courts may order them on a case-by-case basis under their broad discretionary authority. Typically, expert disclosure in Missouri is accomplished through:

• Answers to interrogatories
• Deposition testimony
• Supplemental responses as discovery progresses

In practice, parties should expect to provide:

• The identity and professional background of the expert
• A summary of anticipated opinions
• The basis and reasoning supporting each opinion
• A list of materials reviewed or relied upon

In medical malpractice cases, the procedural rules are stricter. Plaintiffs must file an Affidavit of Qualified Health Care Provider under RSMo § 538.225, certifying that a licensed medical expert has reviewed the case and supports the allegations. This is a statutory prerequisite to pursuing the claim.

Required Declarations

Missouri does not require expert declarations or affidavits as a general part of expert disclosure. However, they are often necessary in support of summary judgment motions under Mo. Sup. Ct. R. 74.04. Any such affidavit must:

• Be based on personal knowledge
• Demonstrate admissibility of facts and opinions
• Confirm that the expert is competent to testify

In medical negligence actions, the RSMo § 538.225 affidavit must be filed within 90 days of filing the petition (complaint), unless the court grants an extension for good cause. Failure to file the affidavit results in mandatory dismissal of the claim.

Fees and Compensation

Expert compensation in Missouri is governed by professional norms and private agreement, without statutory fee caps. However, Rule 56.01(b)(4)(C) requires that when one party seeks to depose another party’s expert, the deposing party must pay:

• A reasonable fee for the expert’s time spent in deposition

Courts may intervene where a fee is deemed excessive or obstructive. Preparation time is typically compensable, especially in technical or scientific cases, but must be reasonable.

Discovery Scope and Limitations

Under Missouri’s Rule 56.01(b)(4), discovery of expert witnesses is permitted through:

• Interrogatories
• Document requests
• Depositions

Parties may obtain:

• The identity and qualifications of the expert
• A summary of opinions and factual basis
• Materials relied upon in reaching those opinions

Discovery of consulting (non-testifying) experts is only allowed under exceptional circumstances—such as when the information is not otherwise obtainable. Additionally, attorney-expert communications and draft reports are not expressly protected by rule and may be subject to discovery unless shielded by the work-product doctrine.

Attorneys should be cautious when sharing documents or strategy with experts, especially in jurisdictions with less robust protections than the federal rules.

Admissibility Standards

In 2017, Missouri adopted a version of the Daubert standard through an amendment to RSMo § 490.065, bringing the state’s evidentiary rule in line with Federal Rule of Evidence 702. Under this standard, expert testimony must meet the following requirements:

1. The expert is qualified based on knowledge, skill, experience, training, or education
2. The testimony will help the trier of fact understand the evidence or determine a fact in issue
3. The testimony is based on sufficient facts or data
4. The testimony is the product of reliable principles and methods
5. The expert has reliably applied those methods to the facts of the case

The court acts as a gatekeeper, and challenges to expert testimony are typically raised through pretrial motions in limine or Daubert hearings. Missouri courts have increasingly excluded testimony based on speculative reasoning, methodological flaws, or lack of scientific support.

Key Deadlines & Strategy Notes

While no uniform statewide deadlines exist, expert-related deadlines are established by court-specific scheduling orders. Common benchmarks include:

• Expert disclosure: Often due 90–120 days before trial
• Rebuttal expert disclosure: Typically due 30–60 days later
• Daubert motions: Must be filed before trial, often 30–45 days prior, per case management order

In medical malpractice cases, the Affidavit of Qualified Health Care Provider must be filed within 90 days of filing the petition.

Strategically, early expert retention and methodical vetting are essential. Missouri courts increasingly scrutinize not only an expert’s qualifications but also the reliability of the expert’s methodology. Attorneys should prepare for admissibility challenges, especially in scientific, technical, or economic testimony.

State-Specific Statutes & Local Rules

• Mo. Sup. Ct. R. 56.01(b)(4): Expert discovery procedures
• Mo. Sup. Ct. R. 61.01: Sanctions for discovery violations, including preclusion
• Mo. Sup. Ct. R. 74.04: Summary judgment affidavits and declarations
• RSMo § 490.065: Standard for admissibility of expert testimony (Daubert based)
• RSMo § 538.225: Affidavit of Qualified Health Care Provider in medical malpractice claims

Local courts—particularly in St. Louis County, Jackson County, and Greene County—may issue case management orders that adjust default deadlines and require more detailed disclosures. Always consult the court’s scheduling order to confirm the timeline.