Partisan Voting on the California Supreme Court

83 Pages Posted: 16 Jul 2020 Last revised: 4 Aug 2020

See all articles by Mark P. Gergen

Mark P. Gergen

University of California, Berkeley - School of Law

David Carrillo

University of California, Berkeley - School of Law

Benjamin Minhao Chen

The University of Hong Kong - Faculty of Law

Kevin M. Quinn

University of Michigan at Ann Arbor - Department of Political Science

Date Written: April 13, 2020

Abstract

When did ideology become the major fault line of the California Supreme Court? To answer this question, we use a two-parameter item response theory (“IRT”) model to identify voting patterns in non-unanimous decisions by California Supreme Court justices from 1910 to 2011. The model shows that voting on the court became polarized on recognizably partisan lines beginning in the mid-1900s. Justices usually did not vote in a pattern that matched their political reputations and party affiliation during the first half of the century. This began to change in the 1950s. After 1959 the dominant voting pattern is partisan and closely aligns with each justice’s political reputation. Our findings after 1959 largely confirm the conventional wisdom that voting on the modern court is on political lines. But our findings call into question the usual characterization of the Lucas court (1987–1996) as a moderately conservative court. Our model shows that the conservatives dominated the Lucas court to the same degree the liberals dominated the Traynor court (1964–1970).

More broadly, this Article confirms that an important development occurred in American law at the turn of the half-century. A previous study used the same model to identify voting patterns on the New York Court of Appeals from 1900 to 1941 and to investigate whether those voting patterns were best explained by the justices’ political reputations. That study found consistently patterned voting for most of the forty years. But the dominant dimension of disagreement on the court for much of the period was not political in the usual sense of that term. Our finding that the dominant voting pattern on the California Supreme Court was non-political in the first half of the 1900s parallels the New York study’s findings for the period before 1941. Carrying the voting pattern analysis forward in time, this Article finds that in the mid-1900s the dominant voting pattern became aligned with the justices’ political reputations due to a change in the voting pattern in criminal law and tort cases that dominated the court’s docket. Together, these two studies provide empirical evidence that judicial decisionmaking changed in the United States in the mid-1900s as judges divided into ideological camps on a broad swath of issues.

Keywords: California Supreme Court, judicial decisionmaking, political reputation, item response theory

Suggested Citation

Gergen, Mark P. and Carrillo, David and Chen, Benjamin Minhao and Quinn, Kevin M., Partisan Voting on the California Supreme Court (April 13, 2020). Southern California Law Review, Forthcoming, University of Hong Kong Faculty of Law Research Paper No. 2020/033, Available at SSRN: https://ssrn.com/abstract=3600566

Mark P. Gergen (Contact Author)

University of California, Berkeley - School of Law ( email )

215 Boalt Hall
Berkeley, CA 94720-7200
United States

David Carrillo

University of California, Berkeley - School of Law ( email )

215 Boalt Hall
Berkeley, CA 94720-7200
United States

Benjamin Minhao Chen

The University of Hong Kong - Faculty of Law ( email )

Pokfulam Road
Hong Kong, Hong Kong
China

Kevin M. Quinn

University of Michigan at Ann Arbor - Department of Political Science ( email )

Ann Arbor, MI 48109
United States

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