An expert witness specializing in one or more scientific areas could provide crucial insight into how the accident happened. Or, put another way, an expert witness is a person with specialized skills, education, knowledge, or experience used in court settings to provide an unbiased opinion or understanding of complicated or technical issues to help the judge and jury decipher what happened. Notably, these opinions and explanations must be tested by (sometimes rigorous) questioning via examination of experts in deposition and trial.
Experts Do Much More Than Testifying in Depositions and Trials
The work of an expert is much more than testifying in depositions and trials and certainly does not involve sitting around and waiting for a needy attorney to reach out. Experts work with many different professions outside of attorneys, such as claims adjustors, risk managers, corporate representatives, business owners, and other experts. Furthermore, testifying in deposition and trial accounts for a tiny percentage of an expert’s work but is certainly the most visible.
Most of the work of an expert involves reading and summarizing a wide array of documents, such as case files, depositions, medical records, geological and architectural surveys, accident reports, and the work of other experts. Additional expert witness work requires project management skills: emailing, answering phone calls, setting up meetings on the video application of choice for the client, talking to other experts, and responding to more emails. In addition to criminal trials/cases, which is the type of work popularized in movies and television shows, experts often work for civil litigation as well. Although the burden of proof for civil and criminal litigation may differ for attorneys, experts are not attorneys. Their proof, or lack thereof, relies on a reasonable degree of certainty in their field, and new information can modify their opinions.
What Makes a Good Expert?
Science is not stagnant but a continually improving process; an expert should maintain current on the research and scholarly literature related to their field. This involves routinely checking the necessary and acceptable scientific databases for their field, including authoritative texts. In the biologically related fields, this involves searching the National Library of Medicine (NLM), which curates the majority of worldwide scholarly research (and not Wikipedia or Google!).
For example, a neuroscientist or addiction expert may know the basis for the molecular mechanism of a drug like cocaine, but research into cocaine is still finding new targets and brain pathways the drug affects. Simply knowing the basic mechanism of cocaine originally published in the early 1990s is necessary for an expert but not sufficient for a full understanding. Importantly, new research has clarified and modified the original cocaine mechanism of action but has not altered the basic premise. Thus, an expert not only has the requisite fundamental knowledge in their field but also must have a continuous working knowledge of important developments.
A good expert is also an excellent teacher and can describe their field to anyone, from other experts and scientists in their field to people with limited or no education, such as those on a jury. In many cases, this involves creating a timeline of events that informs the scientific analysis. Embedded within creating a timeline is the ability to observe the importance of minor details within the case documents and scientific literature that are particularly relevant to the case.
Sir Isaac Newton: How Science, Math, and an Expert Can Describe Observations
Scientists have always tried to explain their observations of the world and how it works based on their particular scientific expertise. In litigation, this is the purpose of an expert witness: someone who looks at the case data and the scientific literature and uses their experience to provide a clear and understandable explanation that is consistent with the science and the observed situation.
Sir Isaac Newton was not content with inaccurate math or science in explaining his observations. In popular mythology, Newton was pondering how to describe the characteristics of an apple falling from a tree, with more humorous adaptations to the mythology involving the apple striking Newton on the head. At the time of Newton, general descriptions of this apple falling depended on a mathematical principle known as algebra. Newton suggested that there is an infinite number of tiny discrete units to describe the fall of the apple, or the motion of any object, over time, and that would be the most accurate description. However, nobody wants to perform infinite calculations to describe a simple phenomenon because then there is no way to describe more complex phenomena. Imagine having a person on the witness stand or in deposition going through algebraic equations longer than the lifespan of all jurors ever! There had to be a better way to describe an observation using science and math.
As a result of the disconnect between the math of the time and his observations of events, Newton invented calculus to describe the objective world accurately! Newton’s theories provided a mathematical and scientific explanation for the observable universe (which, at that time, was largely restricted to Earth and near-Earth objects). In 1687, Newton published Mathematical Principles of Natural Philosophy, which codified his observations using mathematics and science. Since its publication, the first major refining of Newton’s work took nearly 250 years and appeared in 1919 from a German patent clerk named Albert Einstein, termed Special Relativity.
Interestingly, Newtonian descriptions are still accurate for nearly all observations under normal Earthly circumstances but tend to fall apart for very extreme conditions such as those found in outer space or in molecular interactions. In many ways, Newton’s process could be viewed as the basis for the modern practice of expert witness work: using science and math to explain our world. Thus, we can understand how a given scientific or mathematical method can be both accurate and generally accepted but also improved upon without being wrong. These concepts of general acceptance, repeatability, and known error are essential aspects not only for an acceptable scientific theory but also for performing expert witness work.
The Rules and Requirements of an Expert Witness
Federal rules and standards guide the definition of an expert witness and the admissibility of their testimony in courts. An expert is defined by Rule 702 Testimony by Expert Witnesses, which first became law in 1975 as part of the Federal Rules of Evidence. The advisory committee of Rule 702 discussed their intention of a broad definition of an expert and their knowledge, stating that an expert’s knowledge can be scientific, technical, or specialized in nature. Further, an expert’s knowledge can be shared through original research, an explanation of principles, and written opinions that are relevant to the facts of the case. The admissibility of the expert’s testimony depends on the trier of fact to prove that there is a preponderance of evidence supporting the reliability of their testimony. Specifically, Rule 702 states:
A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if the proponent demonstrates to the court that it is more likely than not that:
a. The expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;
b. The testimony is based on sufficient facts or data;
c. The testimony is the product of reliable principles and methods; and
d. The expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.
Frye v. United States
The first admissibility requirements were set by Frye v. United States (1923). In a lower court, Frye was convicted of second-degree murder. During the trial, the court disallowed an expert testimony on a systolic blood pressure deception test that the judge deemed had not gained general acceptance in the field. Frye appealed to the US Supreme Court, which agreed with the lower court that Frye failed to demonstrate that the test was more than experimental in nature. Justice Van Orsdel opined that expert testimony is admissible when “the matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment upon it” and when deductions are made from a principle or discovery that is “sufficiently established to have gained general acceptance in the particular field in which it belongs.”
Daubert v. Merrell Dow Pharmaceuticals, Inc.
Over 50 years later, in 1975, the Federal Rules of Evidence were enacted to provide cohesive guidance on the definition of an expert and admissibility of their testimony. As discussed by the advisory committee, Rule 702 is written intentionally broadly, which led to varied interpretations. The Judge’s interpretation of Rule 702 in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) fundamentally shaped the admissibility requirements into what they are today. Daubert established—what is termed today as the Daubert Standard—that the judge is the gatekeeper for excluding unreliable expert testimony and should consider five factors in determining the reliability and relevance of the testimony to the case. Although these factors are not intended to be a prescriptive list, many times they are used that way. The five factors are whether the technique or theory:
- is objective and has been tested,
- has been peer-reviewed and published,
- has a known rate of error,
- employed properly maintained standards and controls, and
- is generally accepted in the scientific community.
Interestingly, scientists apply many of the same criteria when deciding whether to include data and other papers in their own analyses and synthesis of their work or ideas. Also of note, the term theory mentioned in Daubert refers to what scientists would call a hypothesis or an educated prediction based on the known or available data. The distinction is that a theory is developed in science when a hypothesis has been studied repeatedly from all angles and landed at the same conclusion time and time again and is almost universally agreed upon by all scientists in the field (i.e., the Theory of Evolution). When science arrives at the proof of a theory or the understanding that there is no angle to show that a given description can be disproven, it is termed a law (i.e., the Law of Gravity). Most scientific hypotheses have not been developed into scientific theories, and very few scientific theories have become laws outside of physics or math.
As a result of Daubert, the advisory committee amended Rule 702 in 2000 to designate the judge as the gatekeeper and added criteria for admissible expert testimony. The preponderance of the evidence standard was included in the 2000 amendment but further clarified in a 2023 amendment.
Guidelines for Utilizing Expert Witnesses to Optimize Case Outcomes
An expert witness is a person who has a deep knowledge about a given topic through their specialized skills, education, knowledge, or experience. Their work is largely based on reading and summarizing case documents and scientific literature (and answering emails) and potentially performing re-enactments or experiments to understand a given situation. A good expert should be a skilled communicator who can effectively describe how the science explains real-world observations (like Sir Isaac Newton) and should be as up-to-date as possible on the science of their field. The rules and laws defining an expert are codified in federal and state courts, which act to standardize the acceptability of experts and to help the courts weed out pseudoscience or unproven and untrustworthy methods.
