Public Health Law Map - Beta 5 - Medical and Public Health Law Site

the information being presented is in the form of documents, there must usually be a
human witness to authenticate the documents. Witness’s testimony can be divided
into factual testimony about matters the witness has personal knowledge of and
expert testimony, in which an expert testifies as to conclusions he or she draws from
the records in the case. Most of the controversy about witness testimony concerns
expert witness testimony. Whereas anyone can be a witness to the facts they
personally know, any testimony that requires either an opinion about the meaning of
the facts that is based on a scientific analysis, or otherwise requires special
knowledge not possessed by the average juror, must be presented by an expert. For
example, in a dispute over the sale of land there may be testimony by an appraiser as
to the value of the land. Personal injury cases will need an expert to testify about the
seriousness of the patient’s injuries and prognosis. In medical malpractice litigation,
the plaintiff must present the testimony of an expert who believes that the defendant
did not care for the plaintiff properly and that this breach of professional conduct
caused the plaintiff an injury. A fraud case may require an expert on accounting
standards. A products liability claim against a drug company may require an expert
to testify as to whether the drug actually causes the type of injury that is alleged.
a) Evaluating Expert Witnesses
The key problem with the use of expert witnesses is that the jury is asked to
determine the credibility of the expert testimony presented. In the typical case,
plaintiff and defendant both have experts whose testimony conflicts. The conflict
may be subtle, or simple and direct: the plaintiff’s experts in the breast implant
litigation say that silicone causes autoimmune disease and that women with
implants have a high incidence of autoimmune problems. The defense says it does
not and that women with implants have no more problems with autoimmune
diseases than does a control group. The jury, of course, has been selected to ensure
that no jury members have any special knowledge of medical epidemiology or
autoimmune disease. They must evaluate highly technical, conflicting testimony to
determine billions of dollars in liability.
Jurors cannot evaluate the scientific merits of such testimony. They have no
alternative but to judge the testimony of expert witnesses based on the personal
credibility of the witness. Positive factors such as academic degrees, specialty board
certification, and publications influence credibility. So do factors such as physical
appearance, race, gender, command of English, and personality. For an expert
witness, the foremost qualifications are effective presentation and teaching ability.
The expert must educate the jury in the technical matter at hand, just as he or she
might educate an undergraduate physiology class. The objective is to convince the
jurors that they understand the technical issues. Once there is a perception of
understanding, the expert can convince them that they are making an independent
decision that his or her testimony is correct, rather than just agreeing with him or
her.
The risks of this system are that scientifically or medically unsound evidence,
presented by credible-appearing witnesses, can supplant proper evidence.
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