Emergence of Forensic Psychology as a Recognized Subfield 401Despite psychology’s inability to make any claim of relia-
bility or validity for most of its forensic evaluations, it re-
quired only two decades beyond the founding of AP-LS for
psychologists’ independent forensic evaluations to be com-
monplace in all areas in which clinical expertise was needed
in criminal, civil, and juvenile courts. In many states, by
the 1990s psychologists outnumbered psychiatrists as public-
sector providers of forensic clinical evaluations for com-
petence to stand trial and criminal responsibility (Grisso,
Cocozza, Steadman, Fisher, & Greer, 1994). As we shall dis-
cuss later, the field also witnessed significant growth in re-
search that eventually allowed psychologists to correct many
of the inadequacies inherent in their forensic evaluations
before the 1980s.
New Roles for Psychologists: Expert Witness
Standards of Admissibility for Expert Testimony
Three important court decisions, separated by over 50 years,
and a federal evidence code introduced in 1975 have pro-
vided the basis for evaluating the admissibility of proposed
scientific testimony. As noted earlier, in Frye v. United States
(1923), the District of Columbia Circuit Court ruled that the
results of an early polygraph test were not admissible because
there was not general agreement within the relevant scientific
community about the validity of polygraph results as an indi-
cator of truthfulness. In the court’s words, there was not a
“commonly accepted explanatory theory” that applied to the
polygraph. Hence, the “Frye test” of admissibility depends
upon the general acceptance of a technique or finding within
the scientific community. Over the ensuing years, other psy-
chological expert testimony that has failed the Frye test has
included more complex polygraph techniques and the use of
hypnosis as a memory “refresher.”
The Frye test was one of four criteria that were applied to
proposed expert testimony in an influential decision by the
Ninth Circuit Court of Appeals inUnited States v. Amaral
(1973). The main issue in this case was whether the jury
would receive “appreciable help” from proffered expert testi-
mony on eyewitness research. (It should be noted that not
much solid eyewitness research had been conducted up to this
point.) TheAmaraldecision set out four criteria to determine
helpfulness of the proposed expert testimony: (1) whether the
expert was deemed qualified; (2) whether the testimony prof-
fered was a “proper subject matter” for expert testimony,
meaning that it would provide information that is not already
part of jurors’ “common knowledge” and would not invade
the province of the jury; (3) whether the testimony conformed
to a “generally accepted explanatory theory” (the Frye test);
and (4) whether the probative value of the testimony out-
weighed its possible prejudicial effect. Most subsequent deci-
sions based on theAmaralcriteria have come down against
the admittance of expert testimony on the reliability of eye-
witnesses (Brigham, Wasserman, & Meissner, 1999).
A new evidence code for federal cases, the Federal Rules
of Evidence, was enacted in 1975 after extensive considera-
tion by a prominent advisory committee, the U.S. Supreme
Court, and both houses of Congress. The Federal Rules
describe the criteria for admission of evidence for the entire
federal court system; many states subsequently adopted sim-
ilar codes. The central theme, as summarized by Woocher
(1986, p. 48), is: “Onlyrelevant evidence is admissible, and
allrelevant evidence is admissible in the absence of some
countervailing policy” (italics in original). These relatively
liberal criteria for admissibility are established in Rule 702,
which declares that if scientific, technical, or other special-
ized knowledge would assist the trier of fact (judge, jurors) to
understand the evidence or to determine a fact in issue, then a
qualified expert may deliver expert testimony about the mat-
ter (Federal Rules of Evidence, 1975).
The U.S. Supreme Court dealt with the issue of the admis-
sibility of scientific evidence in Daubert v. Merrill Dow
Pharmaceuticals, Inc.(1993). In addressing the differences
between the Federal Rules of Evidence and the more restric-
tive Frye test, the Court faced questions central to the poten-
tial conflict between science and the law. To what extent
should judges be gatekeepers, screening out “junk science”
from naive jurors who might otherwise be misled or overly
awed by its scientific appearance? Conversely, to what extent
should juries be permitted to serve their traditional role as
fact finders by having access to any evidence that is poten-
tially relevant?
In its decision, the Court focused on the acceptability of
thetechniquesused to gather the scientific evidence rather
than on its “general acceptance” within the scientific commu-
nity (as in the Frye test). The Court discussed the importance
of establishing that the testimony is based on research that
adheres to the “scientific method” and is “not only relevant,
but reliable” (what is described as “reliable” by the justices
would be called “valid” by psychologists). The Court’s deci-
sion discussed several standards for evaluating the research,
including peer review of published work, its testability (or
“falsifiability”), whether it has a recognized “rate of error,”
and whether it is consistent with recognized professional
standards in the area.
Under this decision, judges must evaluate not only the
conclusions but also the methods used by scientific experts.
The Court opined that Rule 702 assigned to the trial judge the
task of ensuring that the expert’s testimony was both reliable