You might think that putting an innocent person in prison for a major crime like rape or murder would end or at least impede a prosecutor's career. But prosecutors are rarely sanctioned for mistakes, even when their misconduct is egregious. In fact, they are often re-elected, promoted to judge, or encouraged to run for political office. Sometimes they even owe these successes to the publicity they get from high-profile convictions of people who turned out to be innocent. Here are some of the worst cases of prosecutors who put more than one innocent person in prison but suffered no significant professional consequences.

The Death Row Gambler

Forrest Allgood, district attorney for four Mississippi counties

Four people Forrest Allgood has convicted of murder were later set free. Two of them served time on death row.

One was Sabrina Butler, an 18-year-old mentally retarded woman Allgood convicted of killing her infant son in 1990. Butler was retried in 1995 after the Mississippi Supreme Court ruled that Allgood had committed misconduct when he told jurors that Butler's refusal to take the stand in her own defense was an indication of her guilt. In the retrial, the medical examiner that Allgood had used the first time around admitted to making some key mistakes, and outside examiners testified that Butler's child likely died of Sudden Infant Death Syndrome or kidney disease. Butler was acquitted and released from prison.

Another Allgood victim was Tyler Edmonds. In Ed-monds' 2007 trial, Allgood posited that the defendant and his sister, Kristi Fulgham, had teamed up to kill Fulgham's husband 13 years earlier. The duo, he argued, had waited until the man was asleep and then simultaneously pulled the trigger. At trial, Allgood called on controversial medical examiner Steven Hayne, who preposterously claimed that he could tell by the bullet wounds in the victim's body that two people had held the gun. On review, the Mississippi Supreme Court threw out Hayne's testimony and ordered a new trial. In 2008 Edmonds was retried, acquitted, and released. Kristi Fulgham was convicted in a separate trial and is still on death row.

In his 1995 prosecution of Kennedy Brewer, Allgood again solicited testimony from Hayne, this time accompanied by Hayne's longtime sidekick, the disgraced bite mark specialist Michael West. West testified that he found bite marks on a 3-year-old murder victim that could only have been made by Brewer's teeth. Based largely on that testimony, Brewer was convicted of raping and killing Christine Jackson, his girlfriend's daughter, and sentenced to death. After the conviction, Allgood attempted to have the biological evidence from the case destroyed. Brewer's lawyer objected and managed to preserve it.

A decade later, more-advanced DNA testing determined that there was semen from two men inside of Jackson, and neither of them was Kennedy Brewer. The state Supreme Court ordered a new trial. Despite the test results, Allgood planned to prosecute Brewer again. When The New York Times asked him why he hadn't bothered checking the crime scene DNA against the state's DNA database, Allgood replied that the state doesn't have such a database. This came as a surprise to the man who had been running it.

Allgood's decision to retry Brewer and his opposition to checking the crime scene evidence against the state DNA database kept Brewer in prison for another six years. When the DNA was finally checked, it revealed Christine Jackson's murderer and showed that he had also raped and murdered another young girl two years later, just a few miles away. Allgood had used Hayne, West, and dubious bite mark testimony in that case too, convicting the wrong man. In 2008, that man, Levon Brooks, was exonerated and freed. The DNA in both cases matched a man named Justin Albert Johnson, who later confessed to both crimes.

Allgood continues to win re-election, and there are still countless people in prison based on his use of Hayne and West. One of them, Eddie Lee Howard, is still on death row.

The DNA Denialist

Michael Mermel, assistant state attorney, Lake County, Illinois

Michael Mermel has a history of standing behind his hunches, even in the face of contrary DNA evidence. In 2005, when a DNA test on an 11-year-old rape and murder victim didn't match his suspect, Mermel argued that the victim must have been sexually active around the time of her murder.

When a DNA test in 2003 showed that the semen in the underwear of a 68-year-old woman didn't belong to Bernie Starks, a man convicted in 1986 of raping and murdering her, Mermel dismissed the results because the semen came from the victim's clothing. Had it come from the woman's vagina, Mermel said, "I would be standing over there advocating the side that the defense has in the case."

Three years later, defense attorneys found the rape kit and tested semen recovered from the woman's vagina. Again, there was no match. Mermel again wouldn't budge, this time arguing that the woman must have had sex with someone else just before the rape.

Mermel's biggest blunder was Jerry Hobbs, who was arrested in 2005 on charges of raping and stabbing to death his 8-year-old daughter and her 9-year-old friend. Hobbs confessed to the killings, but only after 16 straight hours of questioning that began after he'd spent the previous night looking for the girls. The interrogation was not videotaped. Hobbs later retracted his confession and has since claimed he was physically and psychologically tortured by police. The confession was the only evidence against him.

When Hobbs' attorneys revealed in court in 2008 that DNA tests showed the semen found in the mouth, rectum, and vagina of Hobbs' daughter didn't belong to Hobbs, Mermel postulated that the foreign semen must have found its way into the girl's body while she was playing in a patch of woods where teenagers were known to have sex. The girl had been found fully clothed.

Hobbs was finally vindicated in July 2010, when Jorge Torrez was arrested in Arlington, Virginia, for the abduction and rape of a University of Maryland student. When police ran Torrez's DNA against a national database, it provided a match to the semen found in Hobbs' daughter. After five years in jail, Hobbs was released in August 2010.

Mermel continues to serve as a Lake County assistant state's attorney.

The Witch Hunter

Ed Jagels, former district attorney, Kern County, California

Ed Jagels finally retired as district attorney of California's Kern County in 2009. During his 26 years in office, Jagels boasted that the Central Valley district had a higher per capita rate of imprisonment than any other large county in the state. The mock slogan for Bakersfield, the county seat, was "Come for Vacation, Leave on Probation." Yet with crime rates nosediving across the country, the Kern County rate did not fall as quickly as those in neighboring areas.

The boyish-looking Jagels, who was fond of strapping on a gun and tagging along on police raids, was at the forefront of California's disastrous "three strikes" law, which imposed a life sentence on anyone convicted of three felonies. He also led an effort to get anti-death penalty justices removed from the California Supreme Court. He was regularly berated by appellate courts for withholding exculpatory evidence.

Jagels' most egregious transgression was his prosecution of 26 working-class residents of Kern County in the 1980s and 1990s for shocking sex crimes against children. A rash of similar (and, it would turn out, equally bogus) prosecutions was erupting across the country at the time, but Jagels' office in Bakersfield may well have been ground zero. Police and prosecutors told fantastical tales of satanic rituals, orgies, and bestiality, painting gruesome word-pictures of children hung on meat hooks and infants sodomized with knives. None of it happened. Of the 26 people Jagels' office convicted, 25 have since had their convictions overturned. (For a moving account of these cases, see the 2009 documentary Witch Hunt.)

Even as the sex abuse convictions began to fall apart in the mid-1990s, Jagels continued to win re-election. His colleagues selected him to head the California District Attorneys Association. When Jagels finally announced his retirement, Scott Thorpe, the current head of that organization, called him "a prosecutor's prosecutor." An aide to Jagels told The Bakersfield Californian, "Prosecutors from around the state seek and respect his advice on almost every issue of public safety." After retiring, Jagels served as a policy adviser to 2010 GOP gubernatorial candidate Meg Whitman.

The Evidence Hoarder

Kenny Hulshof, former special prosecutor, Missouri Attorney General's Office

For the first half of the 1990s, Kenny Hulshof was the go-to prosecutor when the Missouri attorney general's office needed someone to handle a high-profile death penalty case. He quickly developed a reputation for winning big trials, which he later touted in successful runs for political office.

But in 2010 Missouri Circuit Court Judge Warren McElwain freed a man Hulshof had prosecuted, declaring Dale Helmig innocent of killing his mother in 1993, a crime for which he had been sentenced to death. In his decision, McElwain singled out Hulshof for harsh criticism, accusing him of withholding exculpatory evidence, knowingly presenting false or misleading evidence, and putting evidence before the jury that prosecutors could not prove was true.

That wasn't the first time Hulshof had been reprimanded by a judge for his actions in a murder case. In 2009 Missouri Circuit Court Judge Richard Callahan declared Joshua Kezer innocent of the 1992 murder of college student Angela Mischelle Lawless, criticizing Hulshof for withholding exculpatory evidence and embellishing facts in his closing argument to jurors.

In 2008 an Associated Press investigation found five other cases in which Hulshof was accused of significant misconduct. And in November 2010, the Missouri Supreme Court ordered a new hearing for Mark Woodworth, whom Hulshof convicted of murder in 1995, again finding evidence that should have been turned over to defense attorneys, including a letter from another prosecutor recommending that Woodworth be released due to a lack of evidence.

Hulshof rode his tough-on-crime credentials to six terms in Congress (1997–2009) and ran as the GOP nominee for governor in 2008, losing in the general election. Today he works as a lobbyist for Polsinelli Shughart, a white-shoe law firm with offices in St. Louis, Kansas City, and Washington, D.C.

Three Prosecutors Worth Praising

Many prosecutors, of course, understand that their job is to seek justice, as opposed to convictions by any means. Here are three particularly praiseworthy examples:

The Exculpator

Craig Watkins, district attorney, Dallas County, Texas

With his election in 2006, Watkins, a former defense attorney, became the first African-American D.A. in Texas history. He inherited the office long held by legendary law-and-order prosecutor Henry Wade (the respondent in the landmark 1973 Roe v. Wade abortion case), who was rumored to boast of his ability to convict innocent men.

Upon taking office, Watkins set up what he called the Conviction Integrity Unit, a team of lawyers that works with the Texas Innocence Project to seek out and reopen cases of possibly wrongful convictions. Since 2001, 21 men convicted in Dallas County have been exonerated by DNA evidence—more than any county in the country and more than in all but a handful of states. Watkins' staff also has helped free prisoners in cases where non-DNA evidence has emerged that points to their innocence. There is now a remarkable tradition in Dallas in which former exonerees attend the final hearing of the latest exoneree and welcome him to life on the outside.

In 2010 Watkins was narrowly re-elected, defeating his challenger by a little over one percentage point.

The Snitch Snitcher

Earle Mobley, commonwealth's attorney, Portsmouth, Virginia

In 2009, 28-year-old Ryan Frederick was put on trial for the murder of Chesapeake, Virginia, police Det. Jarrod Shivers, who had been part of a team that broke into Frederick's home during a marijuana raid. Frederick, who had no prior record and who later said he thought he was being robbed, shot and killed Shivers during the raid. Frederick's case turned on whether the jury believed him when he said he feared for his life and had no idea that the men raiding his home were police. During the trial, Prince William County Commonwealth's Attorney Paul Ebert called a jailhouse snitch named Jamaal Skeeter to the witness stand. Skeeter claimed that Frederick had confessed to him in jail that he knew Shivers was a cop and that Frederick had boasted about killing him.

Skeeter was well-known to prosecutors as an opportunist who would say anything to get a break on his own (long) rap sheet. Mobley, a prosecutor, brought this information to Ebert's attention. When Ebert didn't call Mobley as a witness, Mobley reached out to the defense. It was an extraordinary move. It's one thing for a prosecutor to have the integrity to not use unreliable jailhouse informants himself. It's quite another to call out another prosecutor for doing so in the midst of a high-profile trial.

Mobley had warned other prosecutors about Skeeter in the past. He also has filed motions against police officers who miss hearings and publicly reprimanded cops and prosecutors who take shortcuts. "We have a sworn duty as prosecutors to make sure there's a fair proceeding," Mobley told The Virginian-Pilot. "You have to disclose everything under the rules."

Mobley's name also came up in Gene Weingarten's "Fatal Distraction," a moving (and Pulitzer-winning) 2009 Washington Post article about parents who had incomprehensibly but mistakenly killed their young children by leaving them alone in a hot car. While other prosecutors in similar cases had prosecuted the devastated parent, Mobley declined to charge Portsmouth electrician Andrew Culpepper in the death of his two-year-old son. Mobley said police found no evidence that Culpepper intended to kill the boy. He had simply made a crushing mistake. "The easy thing in a case like this is to dump it on a jury, but that is not the right thing to do," Mobley told Weingarten. "I'm not pretty sure I made the right decision. I'm positive I made the right decision." Mobley added that "a prosecutor's responsibility is to achieve justice, not to settle some sort of score."

The Unlikely Reformer

Pat Lykos, district attorney, Harris County, Texas

In 2008 Pat Lykos, a self-described Goldwater-Reagan Republican who supports the death penalty, was elected as chief law enforcement officer of Harris County, Texas, the county that has executed more people than any other, in a state that has executed more people than any other. In fact, under the leadership of former D.A. Johnny B. Holmes—a handlebar-mustached, lock-'em-up tough guy whom the Los Angeles Times once called "the killingest prosecutor" in the country—Harris County by itself sent more people to death row than the 49 states that aren't Texas.

So Lykos would seem to be an unlikely criminal justice reformer. But upon taking office she set up her own team to review prior convictions for mistakes, similar to Craig Watkins' unit in Dallas. Watkins has been aided by a fortuitous historical accident in which Dallas County routinely sent crime scene evidence to a private lab for safekeeping. That means some biological evidence from cases dating back to the 1980s can still be tested. Lykos not only does not have that advantage, but the crime lab in Harris County's largest city, Houston, has a history of mishandling and even destroying evidence.

Nevertheless, Lykos has initiated three exonerations so far. In 2010 the Innocence Project of Texas gave Lykos its Honesty and Integrity in Prosecution Award. The organization's spokesman, Jeff Blackburn, told The Daily Beast earlier this year that "Harris County was the standard bearer of everything bad in criminal justice" until Lykos came along. Under her leadership, Blackburn said, the county "is becoming the single most powerful example of how to change this system and make it work right."

Radley Balko (rbalko@reason.com) is a senior editor at reason.