The U .S. Supreme Court. (Credit: Karen Bleier/AFP/Getty Images.)

In 2000, while running for the Mississippi Supreme Court, Oliver Diaz found himself the target of a well-funded ad campaign.

The U.S. Chamber of Commerce, the national business organization, had spent hundreds of thousands of dollars on ads for and against candidates, provoking calls for an official investigation from Mississippi’s Secretary of State, according to reports at the time. Diaz eventually won, but when he ran for reelection in 2008—then targeted by an organization reportedly founded and funded in part by the pro-gun National Rifle Association—he wasn’t so lucky.

His story highlights how big infusions of outside spending could alter judicial elections. But such spending may have another effect, according to a new report: it may alter the way justices rule.

It seems that “state supreme courts are more likely to rule for the state as the amount of money in high court elections increases,” according to a Monday report by the liberal Center for American Progress. That might be exacerbated by outside spending, according to CAP. Outside groups tend to be more willing to go negative and negative ads tend to focus on voters’ fears, like turning violent criminals loose.

Attacks on Diaz focused on his rulings in cases involving accused rapists and murderers, for example.

“Of course, the irony of that is that the U.S. Chamber’s not interested at all in criminal cases,” he notes.

But motivations aside, outside spending and pro-state rulings seem to go hand in hand, CAP says. The group looked at the seven state supreme court elections in which spending exceeded $3 million for the first time between 2000 and 2007. CAP then compared rulings in the five years before and after those elections.

“The findings were clear: As campaign cash increased, the courts studied began to rule more often in favor of prosecutors and against criminal defendants,” CAP reported.

For Mississippi, 2000 was the year that spending exceeded $3 million. When the next judicial election came up in 2002, justices in the state were ruling against criminal defendants 20 percent more. In its criminal cases, the court favored the prosecution nine of ten times.

(Source: CAP.)

In 2004, the Illinois airwaves were peppered with attack ads featuring violent criminals. That year, the state supreme court favored prosecutors in more than two out of every three cases, 18 percent more than the year before.

(Source: CAP.)

CAP found that the effect was most severe when outside groups were especially active, because they tended to run ads there were more negative.

In Washington and Georgia, the effect wasn’t as pronounced as in Illinois or Mississippi, but the share of rulings against criminal defendants peaked in 2006, the same year both states saw a huge spike in outside spending.

(Source: CAP.)

Other states, such as Wisconsin and West Virginia, saw similar effects, according to CAP. Nevada, the only other state that saw its first judicial election in excess of $3 million in that period, did not. But CAP notes that Nevada was unique in the way the court there hears appeals and in that the first election with spending of more than $3 million was funded by the candidates themselves.

Even former federal Supreme Court Justice Paul Stevens has acknowledged the influence elections can have on rulings.

“Not surprisingly, given the political pressures they face, judges are far more likely than juries to impose the death penalty,” he wrote in a 1995 dissenting opinion.

The apparent trend is troubling, CAP notes, because judicial rulings should be immune to voter pressure. Judges are supposed to base decisions on the law and the facts before them, not what voters want. But as campaign spending continues to grow, pressure to avoid rulings that would play poorly in a 30-second ad continues to mount.