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

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.