An economic rationale for dismissing low‐quality experts in trial
| Published date | 01 November 2017 |
| Author | Chulyoung Kim |
| DOI | http://doi.org/10.1111/sjpe.12129 |
| Date | 01 November 2017 |
AN ECONOMIC RATIONALE FOR
DISMISSING LOW-QUALITY EXPERTS
IN TRIAL
Chulyoung Kim
ABSTRACT
The history of the admissibility standard for expert testimony in American
courtrooms reveals that the standard has gradually increased to a high level fol-
lowing a series of important decisions by the Supreme Court. Whether such a
stringent standard for expert testimony is beneficial or detrimental to the Ameri-
can justice system is still under fierce debate, but there has been scant economic
analysis of this issue. This paper attempts to fill the gap by presenting a game-
theoretic argument showing that a stringent admissibility standard operates to
increase the accuracy of judicial decision-making in certain situations. More pre-
cisely, when the judge faces uncertainty regarding an expert’s quality, the admis-
sibility standard may provide the judge with information about the quality of
expert testimony, thereby increasing the accuracy of judicial decision-making by
mitigating the judge’s inference problem. I show the ways in which this effect
dominates at trial and discuss related issues.
II
NTRODUCTION
Motivation and main results
An important feature of American tort law is that not all experts can testify
in courtrooms. Since a series of decisions by the Supreme Court regarding the
admissibility of expert testimony,
1
experts are required to pass a stringent
admissibility standard to provide testimony on a dispute at trial. In particular,
Federal Rule of Evidence 702 provides that expert testimony that would
otherwise be helpful to the jury is admissible only when (i) the testimony is
based on sufficient facts or data, (ii) the testimony is the product of reliable
principles and methods, and (iii) the witness has applied the principles and
methods reliably to the facts of the case. Thus, Rule 702 is often invoked to
dismiss low-quality experts from courtrooms.
*Yonsei University
1
See Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993), Gen. Elec. Co. v. Joiner,
Scottish Journal of Political Economy, DOI: 10.1111/sjpe.12129, Vol. 64, No. 5, November 2017
©2017 Scottish Economic Society.
445
The aim of this paper is to examine whether dismissing low-quality
experts through a stringent admissibility standard is beneficial for judicial
decision-making. In a model with Bayesian judges, the following questions
arise immediately: if a judge can use Bayesian reasoning, she can extract use-
ful information from even low-quality experts, so why not let the judge inter-
act with any expert regardless of the expert’s quality? Is it not the case that
dismissing low-quality experts only increases error costs because the judge
loses the valuable information possessed by those experts? The answer to this
question is not straightforward in an actual lawsuit in which an expert’s qual-
ity is unknown to judges. In such a situation, the judge is ill-prepared to inter-
act with a testifying expert because the uncertainty about the expert’s quality
imposes an additional constraint on the judge’s Bayesian reasoning, and there-
fore the judge may value some information about the quality of the testifying
expert. This paper shows that a judge can obtain such information when an
admissibility standard is in place.
Employing a stylized game-theoretic model, I show that imposing a strin-
gent admissibility standard on expert testimony entails the following trade-off.
On one hand, as low-quality experts are dismissed from courtrooms, the judge
cannot utilize the information possessed by them, which raises error costs
through the judge’s less precise decision. On the other hand, if the expert
passes the admissibility standard, the judge could obtain better estimates of
the testifying expert’s quality, in which situation error costs decrease through
the judge’s more precise decision. Thus, if the latter effect is dominant, a strin-
gent admissibility standard could increase the ex ante accuracy of the judicial
decision.
The main result shows that the latter effect could be quite strong in certain
types of lawsuits. In particular, it demonstrates that a stringent admissibility
standard could increase the ex ante accuracy of the judicial decision even
when the latter effect is taken to be minimal in the sense that the only infor-
mation available to the judge about the testifying expert’s quality is the very
fact that the expert passed the admissibility standard. Thus, if the judge can
obtain more information about the testifying expert’s quality during expert-
screening processes, it would strengthen my claim that a stringent admissibil-
ity standard could increase the ex ante accuracy of the judicial decision.
Relation to the literature
Legal scholars usually find a rationale for a stringent admissibility standard
from bounded rationality: triers of fact, especially lay juries, are not suffi-
ciently sophisticated and hence are vulnerable to expert bias.
2
Although an
independent expert is presumably neutral to the case under consideration
and willing to provide honest testimony without intentionally withholding
relevant evidence, expert bias may still exist if the expert belongs to a
group that advocates for a particular cause. For example, a cardiologist
2
For example, Bernstein (2008, 2013) argued that the existence of such expert bias justifies
the application of a stringent admissibility standard for expert testimony in trial.
446 CHULYOUNG KIM
Scottish Journal of Political Economy
©2017 Scottish Economic Society
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