The Effects of Ideology on Federal Trial Judges' Decisions to Admit Scientific Expert Testimony

• Author: Jeremy Buchman
• Published date: 01 September 2007
• Date: 01 September 2007
• DOI: http://doi.org/10.1177/1532673X07302339
• Subject Matter: Articles

American Politics Research

Volume 35 Number 5

September 2007 671-693

© 2007 Sage Publications

10.1177/1532673X07302339

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671

Author’s Note: Earlier versions of this article were presented at the 2004 meeting of the

Midwest Political Science Association annual meeting, Chicago, IL and the 2004 meeting of

the American Political Science Association annual meeting,Chicago, IL. The author wishes to

thank editor James Gimpel, Lawrence Baum, Paul Brace, Anke Grosskopf, Melinda Gann

Hall, David Klein, and the anonymous reviewers for their instructive feedback at various

stages of this article. All errors remain the responsibility of the author.

The Effects of Ideology on

Federal Trial Judges’

Decisions to Admit

Scientific Expert Testimony

Jeremy Buchman

Long Island University

This article examines trial court rulings concerning the admissibility of scientific

expert testimony. In Daubert v. Merrell Dow Pharmaceuticals (1993), the

Supreme Court reaffirmed the trial judge’s role as a “gatekeeper” and gave trial

judges substantial discretion over their scrutiny of expert testimony. Because the

external constraints on admissibility rulings are minimal, one might expect that

if trial judges’ideology were to play some role in their decision making, it might

do so here. To test this expectation,I perform a binomial logit analysis of federal

district court Daubert rulings in tort cases from 1983 to 2003. I find substantial

support for the claim that trial judges’ ideology can predict decisions on

admissibility. I find less support, however, for the claim that Daubert affected

trial judges’ willingness to admit such testimony, and no evidence that such

decisions are affected by the prospect of reversal on appeal.

Keywords: judicial behavior; trial courts; political ideology; Daubert

rulings; admissibility of evidence; judicial discretion

Section 1: Introduction

Since the dawn of the behavioralist movement, scholars of judicial

behavior have split on the question of what role ideology plays in explain-

ing judicial, and especially U.S. Supreme Court, decision making. The

perspective that assigns the greatest weight to ideology, the attitudinal

672 American Politics Research

model, has seen its rise to prominence met by a steady stream of criticism

for its portrayal of judicial behavior. Legal practitioners and some legal

scholars have faulted the model for presenting a depiction of Supreme

Court decision making that conflicts strongly with the justices’ perceptions

of their own actions, and in particular for rendering irrelevant such factors

as commitment to a theory of interpretation and respect for precedent. The

scholars most closely identified with the attitudinal model, Jeffrey Segal

and Harold Spaeth (1993; 2002; Spaeth & Segal, 1999), respond by assert-

ing that the traditional legal model, defined in terms of fidelity to case facts

viewed “in light of the plain meaning of statutes and the Constitution, the

intent of the Framers, and/or precedent” (Segal & Spaeth, 2002, p. 48), does

not qualify as a model at all because it lacks falsifiability. Because theories

of textual interpretation fail to produce determinate outcomes across cases,

and precedents can be manipulated so as to provide ostensible support to

either side of a legal dispute, the legal model can justify any outcome and,

as such, lacks explanatory value (Segal & Spaeth, 2002, pp. 48-84; Spaeth

& Segal, 1999, p. xv). According to behavioralists, the justices’policy pref-

erences can explain the bulk of Supreme Court decision making not only on

the merits but also at the certiorari stage.

Among political scientists who study judicial behavior, the attitudinal

model’s emphasis on the influence of unconstrained policy preferences has

been challenged from two broad directions. In one camp are rational choice

theorists who accept the attitudinalists’ assumption of policy-maximizing

behavior but reject the claim that the justices are, in practice, unconstrained

in their ability to further their policy preferences. Instead, the justices must

calibrate their behavior so as to account for the preferences of other actors,

be they fellow justices (see, e.g., Epstein & Knight, 1998; Maltzman,

Spriggs, & Wahlbeck, 2000) or the elected branches of the national gov-

ernment (see, e.g., Ferejohn & Shipan, 1990; Gely & Spiller, 1990, 1992;

Rogers, 2001). In the second camp are “new institutionalists” (Smith, 1988)

who challenge attitudinal approaches on several fronts. Justices might

indeed hold policy preferences, but they also might feel an obligation to

uphold certain norms and expectations with respect to what conforms to

proper judicial behavior (see, e.g., Gillman, 2001; Gillman & Clayton,

1999, p. 5). In this conception, the constraints faced by judges are not lim-

ited to those imposed by external actors; they also include internally

imposed strictures. Viewed in a different light, the relationship between

judges and institutional arrangements is a two-way street: “Judicial behav-

ior is not merely structured by institutions but is also constituted by them

in the sense that the goals and values associated with particular political