An inmate in handcuffs prepares to walk out for a parole board hearing at the New Hampshire State Prison for Men. (Photo by Jabin Botsford/The Washington Post)

Each week, In Theory takes on a big idea in the news and explores it from a range of perspectives. This week we’re talking about the right to a fair trial. Need a primer? Catch up here.

John Pfaff is a professor of law at the Fordham University School of Law in New York City. His research focuses on explaining the causes of mass incarceration, especially the central role prosecutors have played in the process.  

When people think about how our criminal justice system tries to avoid convicting innocent people, they probably think of the second half-hour of a “Law & Order” episode: defense attorneys making motions to thwart the prosecutor, jurors furrowing their brows as they wonder whether the state really has met the high standard of “beyond a reasonable doubt.”

But that’s not reality. In real life, once a prosecutor decides to file felony charges against a defendant, that defendant will almost certainly be convicted — and local prosecutors have a strong incentive to file, likely thanks in no small part to electoral pressures.

[Other perspectives: The presumption of innocence doesn’t apply to my child.]

A study by the Bureau of Justice Statistics looking at urban defendants in state courts found that in 2009, 66 percent of those charged with felonies were convicted, while only one percent were acquitted. The vast majority of those convicted plead guilty instead of going to trial. This means that the last real chance to avoid a wrongful conviction actually occurs at the screening stage, when the prosecutor decides whether to file charges in the first place. And screening is an important part of the process. That same BJS report found that over a third of all cases were dismissed, diverted, or deferred, with almost all of those being dismissed.

We’d like to think that the high conviction rate reflects really good screening, that prosecutors file charges only against those they know are guilty. But nearly 160 death row inmates have been exonerated since the 1970s, and the National Registry of Exonerations — which surely captures only a small fraction of wrongful convictions — runs to more than 1,600 at this point. A study in 1997 (sadly, the most recent of its kind) found that more than 65,000 inmates in state prisons that year had taken “Alford pleas,” which involve pleading guilty while maintaining innocence on the grounds that it is simply too risky to go to trial. Of course, not every Alford defendant is innocent — but then, not every innocent defendant takes an Alford plea.

Clearly, prosecutors do file charges against innocent defendants. The instances that receive media attention tend to be intentionally wrongful, those where the evidence of innocence is overwhelming but prosecutors storm ahead anyway, out of malice or blind ambition.

But I bet most wrongful convictions aren’t the product of such decisions. Prosecutors generally deal with ambiguous cases. What incentives do they face, when acting in good faith, to err on the side of “safety” and file the charges vs. erring on the side of “caution” and dropping the case? Locally elected prosecutors surely do think about innocence, and not just because they don’t want a wrongful conviction scandal to derail a reelection campaign, but there aren’t many restrictions keeping them from filing charges beyond increasingly weakened trial protections and personal ethics.

Prosecution in the United States is a highly local affair. Almost all criminal cases are handled by one of the nation’s approximately 2,400 prosecutor offices, and in 46 states these prosecutors are elected in county-level elections. While prosecutors almost always win their reelection campaigns and often run unopposed, electoral victory isn’t guaranteed. Data indicate that prosecutors running for reelection win 95 percent of the time, but only 69 percent of the time when facing opposition (although that rate rises to almost 80% in larger districts). And several people have reminded me that prosecutors are political creatures, and thus they are sensitive to electoral pressures even when victory seems assured.

So who applies this pressure?

Only a small group: Not very many people vote in these elections. In 2013, for example, a bitterly contested primary battle in Kings County, N.Y., resulted in barely 20 percent voter turnout. And in the 2012 general election in Cuyahoga County, Ohio, 34 percent of those who voted simply skipped voting for prosecutor altogether, despite being in the polling booth already.

Moreover, those who do vote tend to be wealthier, whiter and more suburban, while those who are prosecuted are disproportionately poor, minority and urban. Most cities, for example, are parts of bigger counties that include rings of wealthier suburbs. And these suburbs, as legal scholar William Stuntz has pointed out, tend to wield disproportionate power when it comes to prosecutor elections, even though crime is concentrated in the cities.

Thus the costs of wrongful convictions are disproportionately borne by the group with less political power, or at least a weaker political voice. (Urban minorities are also the biggest beneficiaries of effective crime-fighting by prosecutors, which makes their reduced political voice all the more troubling.)

I’m not saying that this leads prosecutors to willfully go after disproportionately minority urban defendants, innocence be damned (although it certainly helps explain why, say, the current response to rising opioid abuse by whites has been more public-health oriented than the response was to crack cocaine). But it surely means that when deciding whether to file charges in an uncertain case, prosecutors will be more likely to focus on “safety” over “error” — to file rather than dismiss — since the suburban voters want to be safe, but it isn’t their families who bear the costs of error.

Explore these other perspectives:

Keith Findley: The presumption of innocence exists in theory, not reality

Tim Lynch: Americans are bargaining away their innocence

Karen Dolan: The presumption of innocence doesn’t apply to my child

Rebecca Shaeffer: No country has a monopoly on fair trials

Janell Ross: Journalists are supposed to protect the innocent, but it’s easy to fail

Donna Lieberman: We accept assembly-line justice for the poor. But we shouldn’t.