Lawyers rarely do more than minimally review the qualifications of the expert and verify the facts on which the expert conclusions are based.1 The voir dire examination is typically based upon perfunctory questioning about institutional affiliation and publications. The reason for this limited inquiry is simple: most lawyers and judges lack the adequate scientific background to argue or decide the admissibility of expert testimony.1
This article will briefly discuss the basic practical principles of qualifying a witness for expert testimony. An understandable, realistic theory and utilitarian method for expert witness voir dire is provided. The sample voir dire questionsare constructed to obtain that objective2,3— get the witness qualified.
BASIS AND FUNCTION OF EXPERT WITNESS
The expert witness’ existence is created and perpetuated by the legal system. But for the Rules of Evidence, consulting and testimonial evidence would not exist. A simplified restatement of Federal Rules 701–706 (Figure 1) is that a qualified expert may give his opinion to help the court understand evidence, or to establish a fact in issue. States that have not adopted the Federal Rules of Evidence generally have similar rules or statutes governing expert witness qualifications and testimony.
The expert witness performs two primary functions: 1) the scientific function — collecting, testing, and evaluating evidence and forming an opinion as to that evidence;and 2) the forensic function — communicating that opinion and its basisto the judge and jury. A general rule of evidence is that witnesses may onlytestify to what they have personally observed or encountered through their five senses.
SIMPLIFIED RESTATEMENT OF FEDERAL RULES 701–706
701 Lay Opinion: If the witness is not an expert, opinion is admissible only when it is 1) rationally based on perceptions, and 2) helpful to the trier of fact.
702 Testimony by Experts: Expert opinions may be admissible if 1) the testimony assists the trier of fact, and 2) the witness is qualified as an expert.
703 Bases of Opinion Testimony by Experts: Expert opinion may be based on facts or data 1) actually seen or heard by the expert or 2) communicated to him at or before the hearing. Admissibility of the facts or data is not essential if typically relied on in this field.
704 Opinion on Ultimate Issue: An expert may express an opinion which 1) addresses an ultimate issue of fact, but opinions or inferences regarding the mental state of the accused are reserved for the trier of fact, and 2) when that mental state is an element of the crime charged or a defense to that crime.
705 Disclosure of Facts or Data Underlying Expert Opinion: An expert need not provide facts supporting the reason for his opinion unless 1) the court so requires, or 2) asked on cross examination.
706 Court Appointed Experts: The court 1) may issue an order to show cause as to why an expert should not be appointed, 2) may request nominations of an expert by parties, 3) may appoint an expert whether or not the parties agree to that expert, if the expert consents. The witness shall be informed of his duties 1) in writing, 2) a copy of which is filed with the court. The witness shall communicate his findings to the parties, and 1) may be deposed, 2) may be called to testify, 3) may be cross examined, and 3) shall be paid as the court directs. The jury’s knowledge of the court appointment is left to the discretion of the court. This rule does not limit parties from calling other experts.