In California civil cases, expert witnesses are used to provide specialized knowledge or opinions that assist the court in understanding complex issues that are outside the general knowledge or experience of the average person. Expert witnesses are typically brought in to offer opinions based on their expertise in a particular field, such as medicine, engineering, accounting, or psychology. Under California Evidence Code section 801, experts can testify on matters that require specialized knowledge, and their testimony is meant to help the judge or jury understand the evidence more clearly. For instance, in a personal injury case, a medical expert might testify about the extent of the plaintiff’s injuries and the likely long-term effects, while an economic expert might discuss the financial losses caused by the injury.
The use of expert witnesses in California is governed by strict rules, particularly regarding disclosure and qualifications. Parties intending to use an expert witness must provide a written report detailing the expert’s qualifications, the subject matter of their testimony, and the basis for their opinions. This is required by California Code of Civil Procedure section 2034.260, which ensures that both sides are informed about the expert’s potential testimony well in advance of trial. Additionally, experts must be qualified in their field, and their testimony must be based on reliable methods or principles that are widely accepted in their area of expertise. If an expert’s qualifications or methodology are challenged, the court may hold a hearing, known as a “Daubert” hearing, to determine whether the expert’s testimony is admissible. Expert testimony can be a powerful tool in a case, but it must be carefully prepared and disclosed to avoid issues of fairness and reliability.
