On March 28, 2017, Missouri Governor Eric Greitens signed House Bill 153 into law, repealing Section 490.065 RSMo governing the admissibility of expert witness opinion testimony and replacing it with provisions mirroring the expert evidence standard applied in federal courts and the majority of other state courts.

Prior to this revision, often referred to as the "Daubert" standard, an expert's opinion only had to be based on scientific, technical or other specialized knowledge that would assist the trier of fact to understand the evidence or to determine a fact in issue. The facts or data relied upon by the expert to form his opinion only had to be "of a type reasonably relied upon by experts in the field in forming opinions or inferences upon the subject." (Mo. Rev. Stat. § 490.065) 

As revised, Section 490.065 removes the "reasonably relied upon" criteria and replaces it with the heightened requirement that the Court find:

1. The testimony is based on sufficient facts or data;

2. The testimony is the product of reliable principles and methods; and

3. The expert has reliably applied the principles and methods to the facts of the case.

The revision also adopts provisions modeled after Federal Rules of Evidence, Rule 703 ("Bases of an Expert"), Rule 704 ("Opinion on an Ultimate Issue"), and Rule 705 ("Disclosing the Facts or Data Underlying an Expert").

As noted by proponents of the revision, including the Missouri Organization of Defense Lawyers, Missouri Chamber of Commerce and Industry and various medical, insurance and business entities, the revised section aligns Missouri with the standard used in federal courts and the majority of states. It provides a "best practice" whereby the judge acts as a gatekeeper to ensure that expert opinion based only on sound science reaches the jury, helping to increase the reliability of expert witness testimony.

The Missouri Senate passed House Bill 153 on March 15, 2017 (Yes: 21; Noes: 11), and Gov. Greitens signed the bill into law on March 28, 2017.

The Missouri Senate had previously approved legislation on May 25, 2016, adopting the Daubert standard. See MO Senate Bill 591 (2016). That bill, however, was vetoed by Governor Jay Nixon on June 28, 2016.