Evidence: expert testimony.

Existing law authorizes an expert witness to testify in the form of an opinion, if the opinion is sufficiently beyond the common experience such that it would assist the trier of fact and if the opinion is based on matter, whether or not admissible, that is known to the witness prior to their testimony and that may reasonably be relied upon by an expert in forming their opinion in the matter, unless the witness is precluded by law from using those reasons or matter as a basis for the opinion. This bill would create additional requirements for expert opinions regarding medical causation. The bill would, in a case in which an expert testifying about medical causation for the party bearing the burden of proof is required to testify that causation exists to a reasonable probability, allow the party not bearing the burden of proof to offer the testimony of a contrary expert only if the expert can testify that a proffered alternative cause exists to a reasonable medical probability or that a matter cannot meet a reasonable degree of probability in the applicable field, as specified.