How does one become an expert witness? First, a scientist must undergo a process where a judge qualifies him or her as an expert, also known as voir dire. It is during this process that a person’s knowledge, skills, experience, education, and training are established for a judge. The amount of experience required differs based on the judge, the court, and the topic of expertise. Second, expert opinions must be based on reliable information such as journals, reports, textbooks, or personal experience. Next, the knowledge that the expert is providing must assist the triers of fact in understanding the subject matter. Finally, expert testimony must relate to the information beyond common experience and knowledge. Once an expert is qualified, judges must determine if expert testimony is relevant to the case based on the Federal Rules of Evidence. Regarding expert testimony, Rule 702 of the Federal Rules of Evidence (1988) states, “If scientific, technical, or other specialized knowledge will assist the triers of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert ... may testify thereto in the form of an opinion or otherwise.”
It is important for the expert witnesses to exemplify the role of a reporter of facts, not an advocate for one side or another. One should remember that experts are human, so mistakes can and will happen; however, mistakes need to occur as infrequently as possible. Expert witnesses must also have awareness of the perceived weaknesses in their testimony; this may include problems with their training or education, the science, the methods used, or the actual evidence. In addition to these weaknesses, experts must realize that the manner in which they are retained could be used to challenge their testimony. Experts may act as testifying expert witnesses or private consultants, though because many forensic scientists are employed by state agencies, they are typically called by the prosecution. Private experts are sought for their reputation and expertise, and for their ability to analyze and explain the complexities of the science in simple terms for the legal purpose, to present opinions understandably and holes in the opinions of the opposing theory. In addition, consulting expert witnesses are selected based on their work habits, attitude, and personality (e.g., do they easily get along with others?). Potential biases and potential conflicts of interest are the facts to consider for lawyers hiring scientific experts. Though an expert may be affiliated with a state or local agency, it does not mean that he or she will never act in the roles of a defense or private expert. Many scientists keep working in the consultant capacity after retirement.
Court-hired experts (and procedures to do such) support high levels of ethics and competency because in this case experts are evaluated and chosen based on objectivity. In the case of court-hired experts, financial incentives would favor a neutral third party, such as the judge, not the prosecutor or defense. Expert testimony is important in the judicial system because it provides reliable scientific knowledge and relevant information to assist the triers of fact.
Once the experts are qualified based on their credentials, they need to present information and evidence to the triers of fact. It is important that experts present themselves and the evidence appropriately. Experts are teachers; they simplify and explain complex ideas and terms, translate technical language into lay terms, and provide the triers of fact with assistance in the comprehension of scientific and technical issues. Experts are communicators who offer evidence in a clear and concise manner. Personal characteristics that support experts’ success are self-confidence, honesty, competitiveness, and leadership. If experts command a room with quiet confidence, avoid exaggeration and aggression, and gain trust quickly, they are considered excellent witnesses. Testimony that is presented in a clear, concise, and understandable manner with eye contact and proper body language is the goal. Experts should avoid arrogance, argumentative responses, and negativity toward the opposing expert or lawyer. Although providing expert testimony is not an exact science, some learned behaviors make testifying less stressful for experts. Proper public speaking that uses inflection, pauses, gestures, and volume, and does not become monotone is useful in court. Before testifying, experts should have a general understanding of how their area of expertise is pertinent to the case. Experts should prepare for court by reviewing the relevant science, terminology, and standards. Pretrial conferences between the scientist and the lawyers are valuable means of preparation. These meetings help the expert to provide information to the lawyers about what the evidence did and did not show. It also allows the expert to better explain the science to assist the lawyer in preparation for his or her questioning. Such meetings provide the expert with insight into the lawyer’s style of questioning. Although not mandatory, pretrial conferences between the lawyer and the expert benefit both parties in the courtroom. The expert may also prepare for court by reviewing written reports, notes, and case facts. While testifying, it is important that the expert speak directly to the jury to assist the him or her in determining what information is understood and what needs clarification. When answering questions, experts should avoid hearsay, refer to notes only when necessary, have awareness of prior statements given, and answer only what is asked. Lawyers may word questions in a confusing manner to mislead the expert, so it is imperative that the expert listen carefully and take caution with multicomponent questions. If the expert realizes he or she has been misled, the expert should not become argumentative; it is the expert’s duty to remain calm and composed to positively represent the field and the science. Personal characteristics and some learned behaviors assist the expert in successfully conveying scientific information in court.