House Bill No. introduced by A. Nicastro establishes new requirements for the admissibility of expert witness testimony in Montana courts. The bill mandates that before an expert can testify under Rule 702 of the Montana Rules of Evidence, the court must evaluate four specific factors: whether the expert's knowledge aids in understanding the evidence or determining a fact, whether the testimony is based on sufficient facts or data, whether it stems from reliable principles and methods, and whether the expert's opinion reliably applies these principles to the case's facts.

Additionally, the bill includes a codification instruction indicating that the new section regarding expert witness testimony is intended to be integrated into Title 26, chapter 1, part 1 of Montana law. This ensures that the provisions governing expert testimony are clearly defined and accessible within the existing legal framework.