Do Justices Defend the Speech They Hate: An Analysis of In-Group Bias on the U.S. Supreme Court

Published in 2018 in the Journal of Law and Courts 6: 237-262.

Lee Epstein
Christopher M. Parker
Jeffrey A. Segal

For decades now, experiments have revealed that we humans tend to evaluate the views or activities of our own group and its members more favorably than outsiders. To assess convergence between experimental and observational results, we explore whether Supreme Court justices fall prey to in-group bias in freedom of expression cases.  A two-level hierarchical model of all votes cast between the 1953 and 2014 terms confirms that they do. Although liberal justices are (overall) more supportive of free speech claims than conservative justices, the votes of both liberal and conservative justices tend to reflect their preferences toward the speech’s ideological grouping, and not solely an underlying taste for (or against) greater protection for expression. These results suggest the importance of new research programs aimed at evaluating how other cognitive biases identified in experimental work may influence judicial behavior in actual court decisions.

Click here for the article (.pdf)
Click here for the data (Stata .dta file) (posted on January 8, 2018)
Click here for the Web Appendix (.pdf) (posted on January 25, 2018)

The New York Times reported the results of an earlier version of this study. The Times article is here; a summary of the findings prepared for the Times is here. 
Click here for a response to a critique. Appendix C of our response is here (a .pdf file) or here (.xlsx file) (posted on September 30, 2014)
Original data is here (Stata .dta file) (posted on May 2, 2014); Corrected data is here (Stata .dta file) (posted on September 30, 2014)