[Editor's Note: This piece is a response to a forthcoming article in the Northwestern University Law Review by Lee Epstein, Andrew D. Martin, Kevin M. Quinn and Jeffrey A. Segal, titled Ideological Drift on the Supreme Court: Who, When and How Important?, 101 Nw. U. L. Rev. (forthcoming 2007). We posted an introduction to the piece by Epstein et al., 101 Nw. U. L. Rev. Colloquy 127 (2007), http://www.law.northwestern.edu/lawreview/colloquy/2007/8/ (link).]
In their new paper, Lee Epstein, Jeffrey Segal, Andrew Martin, and Kevin Quinn investigate changes in behavior by Supreme Court Justices. They conclude that the policy preferences of most Justices change during their careers, and suggest that this should cause Presidents to reconsider the use of nominations to try to change the direction of the Court. I find the authors' evidence and analysis interesting, but am not yet convinced that any rethinking is in order by the people who pick Justices or care about their selection. I will begin with a general discussion of the model—the Martin-Quinn scores—that the authors use to generate their findings. It is an ingenious method that is attracting some wider interest, but its basis and workings have not yet been presented in a non-technical fashion that is likely to be understood well by a legal audience. One goal of this Essay is to explain it in lay terms. Then I will consider the particular claims the authors make and, finally, their more general thesis about the predictability of behavior by Supreme Court Justices. My two conclusions, in short, are that the authors have not proven that consequential surprises in the Justices' behavior are more common than has been generally supposed; and that the authors' advice to Presidents (and others interested in the selection of Justices) is premature, because the behavior of some Justices is more predictable than that of others, and this itself can often be predicted by asking how firmly the Justices demonstrated their views before joining the Court.