Medicine and Expert Witnesses: Part I

The State of Florida v. George Zimmerman case has definitely captured the attention of our nation.  The case is interesting for many reasons, but the underlying race issue is arguably the most important one.  In addition to the many social issues present, the use of expert witnesses has been a very influential component of this case.  Of special interest to me was the testimony of Dr. Vincent di Maio, the nation’s leading forensic pathologist and expert on gunshot wounds.  Dr. di Maio’s testimony helped to aid the defense in illustrating that Trayvon Martin was on top of Zimmerman when the latter discharged his firearm, going against the prosecution’s claims that the roles were reversed.  Dr. di Maio also indicated that Zimmerman had suffered head injuries from repeated blunt force trauma, furthering the defendant’s claims that he shot Martin in self-defense.

Dr. Vincent di Maio testifying during State of Florida v. George Zimmerman

Dr. di Maio’s testimony, while highly publicized, is not unusual.  Physicians and scientists are often called upon in legal matters to help analyze and interpret evidence.  Their expertise is often so invaluable that cases come down to the results of their inquiries.  The importance of scientific and medical witnesses has inspired curiosity in me.  What is the history of the use of expert witnesses in common law?  Where do scientific and medical expert witnesses fit into our legal code?  Most importantly, how are these witnesses used in current court proceedings, and what are the prospects for the future?

The Origin of Expert Witnesses

The origin of expert witnesses is in England.  Under English law, the first expert witness was used in a 1782 case involving the silting up of Wells Harbor in Norfolk.  In that case, renowned civil engineer John Smeaton testified, signifying the first use of an expert witness’ opinion in common law.  In the United States, expert witnesses were codified into US law in 1975, under the Federal Rule of Evidence (FRE) 702.  The FREs represented general rules passed by congress governing how evidence is presented in both civil and criminal cases.

Scientific and medical witnesses have greatly helped to shape the rules governing expert witnesses.  Prior to FRE 702, rules for admissibility of scientific evidence were established in Frye v. United States (1923).  In Frye, the question at hand concerned whether scientific evidence in the form of a systolic blood pressure deception test was admissible in court.  The Frye ruling indicated that such evidence was admissible as long as the test or theory was “generally accepted” among a meaningful portion of the scientific community.  To prove that something was “generally accepted” parties often put a number of scientific experts on the stand to verify certain tests or theories.  This rule for establishing the admissibility of scientific evidence is colloquially known as the Frye Test.

After the adoption of the FREs in 1975 they along with the Frye Test remained the seminal rules governing scientific expert witnesses.  However, in 1993 a new case would open those rules up to interpretation and eventual amendment.  In Daubert v. Merrell Dow Pharmaceuticals (1993), two citizens born with birth defects sued Merrell Dow Pharmaceuticals claiming that Dow’s drug Bendectin caused their conditions.  Both opposing parties relied upon scientific expert witnesses to prove their claims.  A district court ruled that the testimony from the citizens’ expert was inadmissible because the evidence came from methodologies, such as in vitro and in vivo studies, that were not “generally accepted” at the time.

After the Ninth Circuit Court upheld this decision, the citizens’ took their claim to the Supreme Court.  The citizens’ reasoned that the Frye Test was no longer the governing standard for admissibility of scientific evidence as soon as FRE 702 was passed.  The court agreed, reasoning that since FRE 702 made no mention of “general acceptance” that the Frye Test was not to be applied in discerning the validity of scientific evidence.

The implications of the Daubert ruling were significant in amending the rules for the admissibility of scientific evidence given by experts.  No longer was evidence only judged on its “general acceptance” among the scientific community. Under Daubert, scientific evidence can be admissible if it is “relevant to the task at hand” and “rest(s) on a reliable foundation.”  In determining what makes up a “reliable foundation,” conclusions made from evidence must be based on sound scientific methodology.  Sound scientific methodology rests in using proper scientific method, including empirical testing of evidence, peer review, proper controls, and determination of potential error rates.  In order to prevent the presentation of “pseudoscience,” judges are given the power to be the final arbiter of any submitted scientific evidence.  These guidelines outlined in the Daubert ruling were eventually added as amendments to FRE 702.

Understanding the history of expert witnesses allows us to determine how science and medicine shaped one aspect of the US legal code.  In the next part of this series, I will provide an overview of current medical and scientific involvement in court proceedings.  I will examine not only common case-types in which physicians testify, but case types in which physicians are directly involved in.  Check back soon!