When three Tampa, Florida, police officers were fired for misconduct earlier this year, Hillsborough County State Attorney Andrew Warren put his newly created "conviction review unit" to work. The members pored over 225 closed cases that the officers were involved in, and Warren's office ultimately vacated 17 convictions.

It was a relatively rare move by a prosecutor's office. In less scrupulous jurisdictions, the officers' misconduct might have been concealed under police secrecy laws or the defendants might have been left to challenge their convictions in court, but Hillsborough County is one of the few dozen places in the United States that has a unit dedicated to rooting out bad cases. "In short, we felt that convictions cannot stand based exclusively on the testimony of discredited officers," Warren says.

Conviction review units, also known as conviction integrity units, operate within prosecutors' offices to investigate old cases for errors or misconduct that may have led to a wrongful conviction. The first one started in Dallas in 2007. There are now around 45 across the country, mostly in major cities.

Many district attorney's offices have traditionally operated under a "just win" mentality, measuring their performance by the number of convictions they obtain. Conviction review units are an acknowledgment that public officials can suffer from tunnel vision, confirmation bias, professional ambition, and bureaucratic self-preservation. Left unexamined, these failings can lead police and prosecutors, especially in an adversarial justice system, to dismiss the possibility that they put the wrong person behind bars.

We know that wrongful convictions happen. According to the Innocence Project, there have been 365 DNA exonerations in this country since 1989. Some of the exonerees were awaiting execution. But conviction review units require support and funding—otherwise they're little more than Potemkin projects.

They also need some measure of independence from the larger prosecutorial system. The Hillsborough County state attorney's conviction review unit, for instance, includes a review panel made up of a former Florida Supreme Court justice, a former state appellate judge, and a current appellate judge. Warren says that about half of the conviction review units he's looked at around the country have similar panels.

Another crucial element is buy-in from local law enforcement. "The reality is that we're all doing our jobs because we want to make our community safer and because we believe in justice and fairness," says Warren. "Having innocent people in prison does not advance that mission. They know that, and they recognize that we all make mistakes. We're not perfect, and so just having a mechanism to go back to try to right a wrong that may have occurred is a good thing."

Not all elected prosecutors are so enthusiastic. The Dallas County Conviction Integrity Unit exonerated 30 people between 2007 and 2015 under District Attorney Craig Watkins. Since he lost his re-election bid, however, the only exonerations have been a handful of cases initiated during Watkins' tenure.

The difference between an aggressive conviction review unit and a neglected one is stark. In 2013, Florida resident Eric Wright fired a warning shot at an aggressive ex-girlfriend who burst into his mother's house and refused to leave. Under the state's harsh 10-20-life law for firearm offenses, Wright received a mandatory minimum of 20 years in prison. The trial judge who sentenced him and the appellate judge who upheld that sentence lamented the fact that they had no authority to change it. Even the ex-girlfriend wanted him out of prison.

Wright's attorney approached Jacksonville State Attorney Melissa Nelson's conviction review unit about his case in 2018. The head of the unit suggested Wright file a procedural appeal. Instead of challenging it, Nelson's office then offered him a plea deal to be released on time served.

Although the case was outside the scope of the unit's regular work—Wright's claim was that his punishment was outrageously cruel, not that he was innocent—it was the correct function of a conviction review unit, which should determine not only factual innocence or whether rules were broken but also whether the law was justly applied.

In 2018, there were 151 exonerations in the United States, according to a report by the National Registry of Exonerations. Conviction review units secured 58 of those, even though they only operate in a tiny fraction of the country's roughly 2,300 prosecutors' offices. Imagine how many more people are languishing behind bars for want of government self-reflection.