Forensic, General & Medical
Expert Witnesses

Standards for Scientific Evidence in the Courtroom


Many legal cases are decided based on the available science. DNA and fingerprinting probably jump to mind first, but many other types of scientific evidence make their ways into courtrooms everyday. Understanding the standard necessary to have this evidence admitted and accepted by the court could mean the difference between a winning case and a frustrating outcome.

Many of the tabloid favorite court cases demonstrate just how important scientific evidence can be, both in how it can prove a case and in how its mishandling can destroy an otherwise solid argument. For example, in the OJ Simpson case, DNA evidence could have been the deciding factor in the case, but the mishandling of that evidence caused its usefulness to be overshadowed by the appearance of a taint on its credibility. Similarly, in the Casey Anthony case, the prosecution relied on evidence that was not yet solidly established to try to piece together a case against the defendant. This gave the defense ample room to challenge the evidence and point to its deficiencies as examples of how the state had failed to meet its burden of proof of guilt beyond a reasonable doubt. On the other hand, notorious serial killer Ted Bundy was convicted based, in large part, on the scientific evidence of dental impressions found on his victims' bodies.

But, science surfaces in a variety of court cases, not just criminal ones. For example, it can be critical to patent disputes, product liability claims, construction defect cases, and many more. Modern scientific evidence is largely subject to the admissibility standards described in the US Supreme Court case of Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). The Daubert case directed federal judges to serve as “gatekeepers” of expert testimony and rejected an earlier standard (the Frye test) that required “general acceptance” of a scientific standard, holding that this standard no longer conformed to the Federal Rules of Evidence. In particular, the Court instructed judges to examine the “relevance” and “reliability” of testimony offered by experts.

In the subsequent decision of General Electric v. Joiner, 522 U.S. 136 (1997), the Supreme Court set a high bar for overturning trial judges’ decisions about admissibility of expert testimony, noting that appellate judges must uphold trial judges’ decisions unless they could find that the trial judge committed an abuse of discretion.

Two year later, the Supreme Court again expanded Daubert, noting in its decision in Kumho Tire v. Carmichael, 526 U.S. 137 (1999) that Daubert should apply to all expert testimony, not just that testimony based on science.

Obviously, the standard for scientific evidence is vastly different for the court as opposed to the laboratory. As a result, many critics have pointed out that a great deal of “junk science” is making its way into the courtroom. After all, while judges may be very learned in the law, they are not usually experienced in the various sciences that will be presented in their courtrooms. Differing attitudes among judges and lawyers about different types of scientific evidence have led to inconsistent and inappropriate conclusions. As a result, science which is widely accepted in academic and professional circles as reliable is sometimes not admissible in court, while other science that has been deemed unreliable by practitioners is admitted. Unfortunately, there is not likely to be a better solution to this situation in the immediate future, so expert witnesses must do their best to educate the courts before which they appear in proper scientific method and findings in order to create useful and legitimate precedents for future cases.


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Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer.

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