Feature Stories Campus Events All Stories

Scientific Evidence and the Courts: Solving a Puzzle

For Rebecca Harris, the puzzle begged an answer.

Why, she wondered, was scientific evidence, ranging from DNA to lie detectors, admitted by the courts in some states and not others?

“The science is presumably the same,” Harris says. “But the courts in different jurisdictions have not viewed it in the same way. For instance, Virginia had admitted DNA evidence in 1989 while Minnesota rejected such evidence in 1992.”

So Harris, assistant professor of politics at Washington and Lee University, began gathering and analyzing judicial decisions on scientific admissibility in search of a solution to the puzzle.

Her answer? Politics.

Harris describes the three political patterns that emerged from her research in a new book, “Black Robes, White Coats: The Puzzle of Judicial Policymaking and Scientific Evidence,” which was published by Rutgers University Press.

As she began looking at the differences between the treatment of DNA evidence across jurisdictions, Harris found that some state admissibility standards had set the bar such evidence higher than others, thereby limiting what particular courts could admit.

A second place where she discovered politics at work was in the personal political preference of the judges who were ruling on these cases. She examined both Democrat and Republican judges and found clear patterns from the data.

“The pattern was correlated with who wanted the scientific evidence admitted — the prosecution or the defense,” she says. “If prosecutors wanted admissibility, conservative judges, by and large, found the arguments compelling to allow the evidence. If, on the other hand, a defense attorney wanted to bring the same kind of evidence into a case, the conservative judges were much more skeptical.”

The reverse was true, as well, Harris notes. Liberal judges were much more likely to admit scientific evidence that came from the defense as opposed to being entered by the prosecution.

“Republicans and traditionally conservatives are characterized by law and order politics — strong law enforcement, pro-prosecution. The thought is to get tools in the hands of the government to prosecute these crimes,” Harris says. Democrats and liberals tend to say ‘What about the rights of the accused? We shouldn’t admit evidence in a blanket way just because a police officer says we should.’ They would tilt in favor of making sure defendants have a fair trial.”

The third area in which Harris found politics playing role with the evidence was the presence of third-party reports on the viability of the scientific evidence. When, for instance, the National Research Council issued a report on DNA evidence, that report would often be cited by judges in rendering their decisions depending on what the report concluded, Harris notes.

“My analysis found that these reports tended to side with the prosecution largely because the defense has a hard time generating a third-party report,” she says.

All three of these finds, Harris says, suggest that there is a role for politics in the judicial gatekeeping involved in these decisions about scientific evidence.

As she writes in the book: “Politics can set the bar of admissibility for a jurisdiction, either through legislation or judicial enunciation. Politics can certainly encourage particular courts or judges to favor (or disfavor) a particular science as a function of who it will benefit, defense or prosecution. And politics will certainly determine how respected third-party reports are generated.”

In the final analysis, Harris discounts public criticism of judges as not being able to handle the scientific evidence because they do not have enough background in the science. Instead, she argues that judges, as public servants, are supposed to filter science through our politics.

“I think the judges do a good job,” Harris says. “They understand that even if this is good science, they must also consider the effect it will have on the political system. Even if they are partisan about it, that’s what we need. We need both sides questioning it so that we arrive at a better decision.”