A 2009 study by political scientists at the University of Pittsburgh and Utah State University provides empirical evidence for what we’ve long suspected. From the abstract:
In this paper we address a pressing issue on the contemporary political agenda: Is justice for sale?… We examine decisions by judges on both nonpartisan (Nevada) and partisan (Michigan, Texas) supreme courts in the 2005 term. While we do not find any evidence of a relationship between contributions and the votes of judges in Nevada, it does appear that there is a quid pro quo relationship between contributors and votes in Michigan and Texas. [emphasis added]
The paper’s descriptions of the study’s statistical methods are not for the faint-hearted nonspecialist (“instrumental variables probit model”? “endogeneity”?), but the paper’s literature review contains several gems:
In 2001, Justice at Stake conducted a survey of over 2,400 state judges. They found that 26% of judges thought that campaign contributions had at least some influence on the decisions of judges…. Additionally, 56% of state judges believe that judges should recuse themselves from cases involving contributors.
… a 2007 Zogby survey of business leaders indicates that 79% of them believe campaign contributions have at least some influence on the decisions of judges…. Moreover, 93% strongly agree that judges should recuse themselves from cases that involve campaign contributors.
… A 2004 nationwide survey [of voters] by Justice at Stake showed that 71% of respondents believed that campaign contributions had at least some impact on judges’ votes. More recently, a 2008 Justice at Stake survey of Minnesotans revealed that 59% of them believe that campaign contributors have at least some influence on judicial decisions; a similar survey of voters in Wisconsin yielded a figure of 76%.
The paper concludes that “the people are correct that judges are influenced by campaign contributions.”