OVERVIEW OF EXPERT TESTIMONY

1. The topic of expert witnesses and the scientific and technical evidence they bring into the trial, is a complicated one. In many law schools, this topic is the subject of an entire advanced evidence class. There are whole casebooks devoted to this subject alone, and the leading reference book (Faigman, Kaye, Saks & Sanders) is 4 volumes. We will give it only cursory coverage here. There is not time to do more in an introductory evidence class.

2. Rules 702-706 govern expert testimony.

3. Analyzing the admissibility of expert testimony consists of asking four questions:
A) Is there an appropriate issue for expert testimony? Rule 702 says that experts may testify only "If specialized knowledge will assist the jury." This is the equivalent of the "helpfulness" foundation for lay witness opinions.
B) Does the proposed witness have the qualifications to be an expert? Rule 702 says that the witness must be "qualified as an expert by knowledge, skill, experience, training or education." As with other foundations, only minimal qualifications are required.
C) Is the expert basing opinions on adequate information? Rule 702 requires the testimony to be "based on sufficient facts or data." The expert must base his or her opinion on enough information, observations, tests, experiments, and other data to make them reliable. However, experts do not need personal knowledge. They may review files and records and offer opinions as consultants.
D) Is the expert's opinion rational? Rule 702 requires an expert's testimony to be "based on reliable principles and methods ... applied reliably to the facts of this case." To meet this requirement, the expert testimony must:
-- be confined to the expert's area of expertise
-- be rationally related to data
-- not contradict basic scientific principles
-- be derived by following accepted procedures, practices and protocols in the field
-- and be "scientifically reliable" as defined by the Daubert test.

4. The concept of "scientific reliability" (also known as the "Daubert" test) derives from Daubert v. Merrell-Dow, discussed at 366 et seq, in your text. Basically, the Supreme Court said that opinions that are scientifically reliable will be more helpful to the jury than opinions based on advertising, quackery, abstract philosophy, or outright fraud.

5. Daubert says the judge makes the determination of scientific reliability, based on the evidence presented by the opposing parties. The courts are therefore faced with a difficult task -- they must distinguish "true" scientific knowledge from "false" science. Is this a good idea? Do you think judges have extensive scientific background? I don't. Most judges were probably business, finance, or political science majors as undergraduates, and then went to law school and have never taken a science course in their lives after high school biology, which (if it was anything like mine) was devoted entirely to dissecting frogs because school officials were afraid to anger fundamentalist Christians who objected to everything else in the science curriculum.

6. The Supreme Court tried to help these poor judges in the Daubert case by giving them suggestions on what to look for. They didn't think these up themselves, but took them from amicus briefs filed by scientific organizations. To be reliable, matters of science must:
A) Be derived from scientific methodology -- that is, theories tested by neutral scientists through controlled studies.
B) Be subjected to peer review and publication -- no "private" or proprietary data;
C) Have a small rate of error in results (no statistical significance of results unless p<.05.
D) Have achieved widespread acceptance if it has been around for awhile (Among educated elite -- not among general public -- e.g., evolution).

7. The courts have not consistently extended the "reliability" concept to non-scientific fields. It is clear that expert opinions in quasi-scientific fields like engineering and medicine must be scientifically reliable, but what about such well-known types of expert testimony as handwriting analysis, accident reconstruction, and chiropractic? Courts have generally used a two-part test: first, has science shown the field to be unreliable (e.g., parapsychology)? If so, no opinions allowed. Second, if the field is one in which expertise is accumulated from experience and science is not involved (e.g., auto mechanics), the opinion must be reliable as that term is defined within the field.