MO SB233

Repeals and replaces Section 490.065, RSMo, establishing new standards for expert witness testimony in Missouri courts

Expert witnesses must meet four criteria: specialized knowledge that helps the trier of fact, testimony based on sufficient facts or data, testimony using reliable principles and methods, and reliable application of those methods to the case facts

Experts may base opinions on facts or data they observed or were made aware of; inadmissible underlying facts may only be disclosed to the jury if probative value substantially outweighs prejudicial effect

In criminal cases, expert witnesses are prohibited from stating opinions on whether a defendant had the mental state constituting an element of the crime or defense—those determinations are reserved for the trier of fact alone

Experts may state opinions and reasons without first testifying to underlying facts, but may be required to disclose those facts on cross-examination