Anthony Caravella was released from a Florida prison last month. He served 26 years for a rape and murder that DNA testing has shown he didn't commit. Caravella was 15 at the time he was arrested, and has an IQ of 67. He was convicted in part due to a confession his attorneys say was beaten out of him by police interrogators. Caravella's prosecutor, Robert Carney, has put at least two other people in prison for murder who were later cleared of the crimes for which they convicted. Carney is now a judge in Broward County, though he recently announced he's retiring at the end of this year.

The injustice in Caravella's case could have been worse. Carney originally sought the death penalty. The jury voted 11-1 for life in prison, instead. According to the Sun-Sentinel, in 1985 Carney also prosecuted another mentally-challenged man, John Purvis, for killing his Ft. Lauderdale neighbor. Months later, Carney received a tip that the victim's ex-husband had hired a hit man to kill her. Carney refused to reopen the case, leaving Purivs' attorneys to hear about the murder-for-hire through other means. Purvis did nine years in prison before the woman's ex-husband and the hit-man were arrested and prosecuted.

In 1981, Carney convicted another man, Christopher Clugston, for murder based on testimony from an informant who later recanted. In 1994, Clugston was cleared and released from prison by Florida Gov. Lawton Chiles, but on the condition he never return to the state. Clugston also left prison with AIDS, the result of a gang rape while he was incarcerated.

Howard Finkelstein, the public defender in Broward County, Florida, said of Carney to the the Sun-Sentinel newspaper, "I cannot think of another prosecutor anywhere in the U.S. that has put away three innocent people in separate cases."

Actually, it could be four. Carney also participated in the prosecution of Frank Lee Smith, convicted in 1986 of a rape and murder based on the testimony of a single eyewitness. Smith died of cancer on death row in 2000. Ten months after his death, DNA testing cleared Smith of the crime. In all, seven men have been wrongly convicted of murder by the state's attorney's office of Broward County.

As DNA exonerations continue to accumulate across the country, we're left with some tough questions about accountability for the public officials who put innocent people in prison. Certainly in some cases honest mistakes can be forgiven. But what about cases, like that of John Purvis, where a prosecutor illegally withholds evidence of a suspect's innocence? What about prosecutors who participated in multiple wrongful convctions? Is it fair to hold them accountable years or decades later? What of those who went on to become judges, and now preside over murder cases?

There are other Robert Carneys. A couple of months ago, I wrote about Daniel Ford, a former prosecutor, now a Massachusetts Superior Court Judge, who may have withheld evidence and committed other misconduct in his prosecution of Bernard Baran for child molestation. Baran was cleared of the charges and released earlier this year after serving 26 years in prison. Ford has never been investigated, much less disciplined, for his role in putting Baran in prison.

As an assistant district attorney, Mississippi Judge Bobby DeLaughter helped hide exculpatory evidence in the case of Cedric Willis, wrongly convicted of a rape and two murders. Willis served 12 years for a crime he didn't commit, despite DNA evidence pointing to his innocence. While Willis sat in Parchman Penitentiary, much of his time in solitary confinement, DeLaughter was elected a judge. Last summer, DeLaughter himself plead guilty to lying to federal investigators looking into a corruption scandal. But he was never punished for the misconduct that sent an innocent man to jail.

Then there's Forrest Allgood, the Mississippi district attorney with a record that puts him in company with Carney. Allgood prosecuted both Kennedy Brewer and Levon Brooks, each convicted of raping and killing young girls in Mississippi in the early 1990s. Allgood relied on the testimony of disgraced bite mark specialist Michael West to secure those convictions. Even after DNA testing cleared Brewer in 2000, Allgood pointed to West's match of bite marks on the victim's body to Brewer as evidence that Brewer must have participated in the crime, even if he didn't actually commit the rape. Brewer remained in prison an additional seven years. Brewer and Brooks were finally released in 2007 after a check of the state's DNA database (which Allgood tried to prevent) showed a single man committed both rapes and murders.

Two other people Allgood has convicted of murder were later given new trials and acquitted. Tyler Edmonds, who was 15 at the time he was charged, was convicted based on a confession Edmonds says was coerced and by implausible forensic testimony from disgraced Mississippi medical examiner Steven Hayne. Allgood also convicted 18-year-old Sabrina Butler, who is mentally challenged, of killing her infant son. Butler was sentenced to death. The state supreme court also tossed out her conviction, which also relied in part on bad forensic evidence.

Allgood hasn't (yet) been elected to the bench, but he continues to be reelected as district attorney.

Something is wrong here. It may well be true that the prosecutors noted above represent a tiny minority of those who serve or have served in the position. But whatever the number of "bad apples," our criminal justice and political systems seem unconcerned about weeding them out. Instead, they're often rewarded and promoted, despite long records of incompetence and misconduct. In fact, in the sense that misconduct can help win convictions, such prosecutors are often rewarded because of it. The Innocence Project estimates that prosecutorial misconduct factored into about a fourth of the wrongful convictions handled by the organization. Yet in none of those cases did a prosecutor face any serious sanction.

Be it through state bar association actions, judicial investigations and discipline, or legislation creating some other means of oversight, bad and incompetent prosecutors need to be held to account. When a prosecutor perpetrates misconduct or demonstrates incompetence that sends an innocent person to jail, it's a regrettable but understandable product of the fact that that any large system is going to have bad actors. But when that prosecutor remains free to go on prosecuting other cases, with no repercussions, the very legitimacy of the criminal justice system is called into question.

Radley Balko is a senior editor at Reason magazine.