CA Bill Proposes Higher Standard for Scientific Expert Testimony

    In the California Senate, a lawmaker recently introduced CA Senate Bill 243 in an effort to both heighten the evidentiary standard of scientific testimony as well as decrease the admission of false evidence against criminal defendants. Proposed by Senator Scott Weiner, the bill is designed to ensure the accuracy of expert witness testimony while also combatting wrongful convictions. With suggested additions and amendments to California’s Evidence Code and Penal Code, the bill would have a drastic effect on defendants seeking to file writs of habeas corpus—petitions through which their convictions and imprisonment are challenged as unlawful. In light of the current, notoriously high evidentiary burden in succeeding on a habeas corpus petition, SB 243, also referred to as “The End Wrongful Convictions Act,” has the potential to significantly change the criminal justice process and its use of expert testimony.

    Changes to California’s “False Evidence” Definition

    Under California’s current laws, criminal defendants may file a writ of habeas corpus challenging their conviction for a number of reasons pursuant to Section 1473 of the California Penal Code. This includes challenging false evidence introduced against the defendant that is “substantially material or probative on the issue of guilt or punishment.” Existing law defines false evidence to include expert opinions that “have either been repudiated by the expert who originally provided the opinion…or that have been undermined by later scientific research or technological advances.” Such laws protect defendants from experts that subsequently change their opinions and/or advancements within the field that, thus, deem the expert’s previous opinion at trial to be incorrect.

    Senator Weiner’s bill would further expand the definition of false evidence in the context of expert testimony. The law would be amended to define false evidence as the “opinions of experts that have either been repudiated by the expert who originally provided the opinion at a hearing or trial or that have been undermined by scientific research, including scientific research that existed at the time the expert’s testimony was given, technological advances, or the emergence of a reasonable dispute with the expert’s relevant scientific community as to the validity of the methods or theories upon which the expert based their opinion.

    In other words, expert testimony can be deemed false, for the purposes of a habeas corpus petition, without the opinion necessarily being completely rejected by the scientific community. Rather, there need only be a “reasonable dispute” as to the methodologies or theories of the underlying opinion. The expansion of the kinds of expert opinions that may be considered false will undoubtedly call into question California’s current admissibility standards.

    How Will the Admissibility of Expert Testimony Change?

    The definition of false evidence in the context of expert testimony cannot be changed without also changing the standard by which such evidence is admitted at trial. The proposed legislation seeks to add Section 806 to California’s Evidence Code, which would require any criminal court to determine whether “any underlying literature, studies, research, and other materials on which the expert relies in forming that opinion, are based on a reliable foundation, proper methodology, and sound logic.

    Currently, California applies the Frye standard when admitting expert testimony, that is, the court determines whether the expert’s opinion is generally accepted within its scientific community. However, case law throughout the years has recognized the judge’s role as a “gatekeeper” when admitting expert testimony. California has not yet adopted the competing Daubert evidentiary standard, which enumerates factors to consider, such as the expert’s reliability and methodology. Interestingly, the proposed Section 806 is more akin to Daubert, in that it focuses on how an opinion is formed.

    If passed, the language in this bill may result in a more proactive criminal court that takes into account a variety of factors when determining the admissibility of expert testimony. At the same time, the courts will be tasked with determining the reliability of a wide range of scientific data—a role which some may argue is too technical for one that does not practice in the particular field.

    The Effect on Expert Testimony in Criminal Trials

    “The End Wrongful Convictions Act” bill came to fruition as part of a larger effort to reform the criminal justice system. Inaccurate expert testimony and faulty forensics are the biggest causes of California’s wrongful convictions. Currently, there are an estimated 200 defendants serving lengthy prison sentences for which they were wrongfully convicted. As Senator Wiener explains, the proposed legislation “gets us one step closer to ensuring no one is sent to prison for a crime they did not commit, and it will allow those wrongfully convicted to seek freedom…Expert testimony should be based on accurate scientific facts and logic, and we need to stop allowing unreliable expert witness testimony.”

    Although all expert testimony will potentially be subject to a different standard under the bill, its purpose focuses on the quality of forensic science, or lack thereof, in criminal trials, such a fingerprint or bite mark evidence. The National Academy of Sciences had previously highlighted this issue in a 2009 report which found that the quality of forensic evidence—evidence that is typically looked upon by a jury with deference—varied widely between jurisdictions. Notably, the Academy’s findings also called into question the veracity of fingerprint evidence—once the “gold standard for forensic scientists”—concluding that such evidence is susceptible to confirmation bias by the police (i.e., the results are based on what the police already believe).

    But, ultimately, the proposed legislation is not an indictment of all expert testimony. Rather, it seeks to ensure that the weight juries so often give experts is, in fact, warranted.