The Art of Opinion Testimony in California Criminal Trials

In the criminal law, the admission of opinion testimony can be a powerful tool for both the prosecution and the defense. Opinion testimony, governed by California Evidence Code sections 800-805, allows witnesses to express their opinions in court. There are many nuances of opinion testimony depending on the individual who is testifying.

Lay witnesses, often regular individuals without specialized expertise, are generally permitted to offer opinions in certain situations, provided the opinions: (1) are rationally based on the witness’s perception; (2) are helpful to the understanding of the testimony or determination of a fact in issue; and (3) are not based on scientific, technical, or specialized knowledge.

For example, in a robbery trial, a witness who was present at the crime scene may be allowed to provide an opinion on the identity of the perpetrator. The witness’s opinion is based on their perception and could be deemed helpful to the jury in identifying the defendant. An objection to this testimony would be overruled.

However, where a lay witness attempts to give an opinion on a suspect’s motive for the crime, the objection may be sustained. The opinion might not be rationally based on the witness’s perception or could stray into an area requiring specialized knowledge. An objection to this testimony would be sustained.

Expert witnesses, on the other hand, possess specialized knowledge or experience that enables them to offer opinions on complex matters. To qualify as an expert, a witness must meet several criteria. (1) The witness must have sufficient expertise or specialized knowledge; (2) the witness's testimony must be based on reliable principles and methods; (3) the testimony must be relevant to the case; and (4) the witness must apply their expertise to the particular facts of the case.

For example, in a murder trial, a forensic expert may provide an opinion on the cause of death based on autopsy results and medical expertise. The expert's opinion is relevant, based on reliable principles, and applied to the case's specific facts. Any objection to this testimony after the attorney lays the foundation for that witness’s expertise would be overruled.

However, if the same forensic expert attempts to provide an opinion on the defendant’s guilt or innocence, the objection may be sustained. Determining guilt is not within the purview of forensic science, and it goes beyond the scope of their specialized knowledge. An objection to this statement would be sustained.

Specialized Knowledge: The key distinction lies in the witness’s expertise.

Relevance: Expert opinions are highly relevant when addressing complex or technical matters, whereas lay opinions are more common in situations where personal perception aids in understanding.

Helpfulness: Expert opinions are accepted when they can assist the trier of fact in understanding complex issues, while lay opinions are admitted to help with matters within the common experience of jurors.

Relevance: If the prosecution attempts to introduce expert testimony of a veterinarian in a trial child abuse trial, a relevance objection would be sustained.

Lack of Expertise: When a witness claims to be an expert accountant in a wire fraud case but it later turns out that the witness never graduated high school and lacks the requisite specialized knowledge, an objection would be sustained.

Hearsay: If a lay witness offers opinion testimony that relies upon a statement they heard from another customer at a convenience store that was robbed, a hearsay objection would be sustained.

Speculative or Conclusory: If a lay or expert witness provides a speculative or conclusory opinion without a rational basis or reliable methodology, such as a psychic testifying that she foresaw an incident of domestic violence, an objection on speculation grounds would be sustained.

If you are facing charges for a crime, it is critical that you hire an attorney that understands the nuances of opinion testimony. As a former Deputy District Attorney with over 14 years of prosecutorial experience, Los Angeles criminal defense attorney Michael Kraut has extensive experience both direct and cross examining witnesses who offer their opinions about matters in criminal cases.

For more information about the criminal justice process, and to schedule your free consultation, contact Michael Kraut at the Kraut Law Group located at 6255 Sunset Boulevard, Suite 1520, Los Angeles, CA 90028. Mr. Kraut can be reached 24/7 at 888-334-6344 or 323-464-6453.