Using Expert Accident Reconstruction Evidence at Trial

Woodland Hills Trial Attorney Barry P. Goldberg addresses questions relating to trial tactics and admissibility of expert accident reconstruction evidence on a regular basis. First, in order to lay the foundation to admit expert reconstruction evidence, an expert must show the court that the evidence is relevant and that expert testimony is based on the expert’s knowledge, experience, and background in the particular field relevant to the case. Second, the expert must show that a computer crash program and the input data is considered relevant and non-speculative at trial. Third, the expert must show whether demonstrative flip charts are considered computer animations or computer simulations.

1. What is required for expert testimony to be admissible in court?

Attorneys may rely on expert testimony based on the expert’s knowledge, experience, and background in a particular field that is at issue in a case. Typically, trial courts use Evidence Code sections 801 and 802 which states that the trial court must “exclude expert opinion testimony that is (1) based on matter of a type on which an expert may not reasonably rely, (2) based on reasons unsupported by the material on which the expert relies, or (3) speculative.” (Sargon Enterprises, Inc. v. University of Southern California (2012) 55 Cal.4th 771-72). As such, an expert may testify about the materials he received, how he applied his education and experience in reaching his opinions. Further, an expert may use hypothetical possibilities to determine the speed of a driver at the time of the accident because it is based on an expert’s knowledge, experience, and education. This can be helpful to the jury to understand an issue in a case when the court admits expert evidence to prove whether the testimony of the parties is corroborated by expert testimony and expert reconstructive evidence.

2. Is the computer crash program and input data provided by an expert considered relevant and non-speculative at trial?

For the court to admit expert testimony, an expert must identify the materials he relied on, such as, research studies in determining the normal range of acceleration from a stop sign and the expert’s educational background. For example, the expert may testify at a hearing that they were registered in California as a professional mechanical engineer who had been working in accident reconstruction analysis for more than 30 years. Further, the expert may testify the “known parameters” they relied on that came from years of experience. The expert may indicate that the parameters came from National Highway Traffic Safety Administration crash test data. Lastly, the expert may identify journals that he regularly reviews for published studies and crash test results, like “Collision” and “Accident Reconstruction”. As such, an expert’s assumptions may be based on observable facts supported by the evidence by the expert’s knowledge and experience. Even if the expert input values of the PC-Crash software are not an ideal match between the simulated accident and the evidence of damage sustained by the cars, still, it goes to the weight of the evidence and not the admissibility of the expert’s testimony. Therefore, the expert testimony is admissible since lack of certainty does not justify exclusion of the opinion in its entirety.

3. Are Flip Charts that are demonstrative evidence considered computer animations or computer simulations?

Flip charts may be admitted into evidence as demonstrative evidence as a tool to aid the jury in understanding the substantive evidence. An example of demonstrative evidence includes maps, charts, and diagrams which illustrate a witness’s testimony. “Flip charts” are visual representations of an expert’s models of the accident based on whether a driver was traveling 35 miles per hour or 25 miles per hour. According to the Rutter Group, “Demonstrative evidence is physical evidence that is not itself at issue in the case but which illustrates or demonstrates a party’s testimony or theory of the case.” (Wegner et al., Cal. Practice Guide: Civil Trials and Evidence (The Rutter Group 2019). An expert’s flip charts may be admitted if an expert testified about the flip chart and the flip chart is either considered a computer animation or computer simulation. According to People v. Duenas, computer animations that are merely used to illustrate an expert’s testimony is admissible if “it is fair and accurate representation of the evidence to which it relates” (2012) 55 Cal.4th 1, 20.) By contrast, “computer simulations that contain scientific or physical principles requiring validation are admissible only after a preliminary showing that any ‘new scientific technique’ used to develop the simulation has gained ‘general acceptance . . . in the relevant scientific community.’” (Id. at p. 21, citing People v. Kelly (1976) 17 Cal.3d 24, 30.)

In conclusion, expert accident reconstructive evidence is admissible when the expert testifies about the PC-crash software and the expert’s assumptions were based on observable facts supported by the evidence by the expert’s knowledge and experience.

If you have any questions about your case, or the admissibility of accident reconstruction testimony, trial tactics, contact Woodland Hills Trial Lawyer Barry P. Goldberg right away.