PaperTrail has some homework for Supreme Court justices, regarding Caperton v. Massey, a case they heard arguments for yesterday. A recent study looks at the connections between campaign contributions and judicial decisions, which is at the heart of the case. The results, in case they don’t have time to read the full report, show that contributions do indeed appear, in some cases, to influence decisions.

At issue in the Supreme Court: when judges should recuse themselves in questions of judicial bias. In Caperton v. Massey, West Virginia Justice Brent Benjamin refused to remove himself from deliberations affecting the Massey Coal Company whose top executive spent $3 million on ads attacking his opponent in the race for a State Supreme Court seat. In the past, Benjamin had ruled against Massey on five separate occasions.

The new study, “The Effect of Campaign Contributions on Judicial Decisionmaking,” by Chris Bonneau and Damon Cann, tracked state-level Supreme Court decisions in Nevada, Michigan, and Texas. In both Michigan and Texas, states where judges affiliate with a political party, the authors found evidence of a quid pro quo relationship. In Nevada, which has a non-partisan election system, the study found no evidence of a connection between contributions and votes.

For what it’s worth, West Virginia Supreme Court judges are chosen in partisan elections.

Similarly, a 2006 New York Times survey of the Ohio Supreme Court reports that justices voted in favor of their contributors 70 percent of the time, and almost never disqualified themselves from hearing contributors’ cases.

Over the past decade, judicial race spending has nearly doubled, casting the question of judicial independence into sharper relief. As Ohio Supreme Court Justice Paul E. Pfeifer, a Republican, memorably puts it, “I never felt so much like a hooker down by the bus station in any race I’ve ever been in as I did in a judicial race.”