Throughout the 1990s, senior New Orleans prosecutor Jim Williams kept a model electric chair on his desk. The chair held photographs of five African-American men his office had helped place on death row. He considered it a major achievement and was pictured with the chair in a 1995 issue of Esquire magazine.

Years later he was quoted in a Los Angeles Times article, saying of his career as a prosecutor: “It got to the point where there was no thrill for me unless there was a chance for the death penalty.”

Of the men photographed, two have since had their sentences commuted to life, one won at a retrial, and two have been exonerated.

On Tuesday, John Thompson, one of the exonerated men, filed a 29-page complaint with the Justice Department. Thompson, 54, petitioned for a federal investigation of what he and his lawyers call “a pervasive and unapologetic pattern of unethical improper conduct” perpetrated by Williams and his colleagues at the Orleans Parish District Attorney’s office.

Thompson served 18 years, most of them in the notoriously violent Angola Penitentiary after being found guilty of a murder he did not commit. He spent 14 of those years on death row until — weeks before one of his seven proposed execution dates — a team of pro bono lawyers discovered that prosecutors led by Williams had failed to disclose blood samples from the scene of the crime at Thompson’s original trial. Those samples showed that the perpetrator had type B blood. Thompson has type O blood. Eventually Thompson was granted a retrial and, in 2003, a jury took 30 minutes to find him not guilty.

Thompson went on to sue the Orleans Parish District Attorney’s office for failure to train its prosecutors and won a jury award of $14 million — one for each year he spent on death row — only to have that verdict overturned by a controversial 5–4 U.S. Supreme Court decision. While prosecutors conceded they had withheld evidence supporting Thompson’s likely innocence, the court held that the district attorney’s office could not be found civilly liable because the mistake by prosecutors did not stem from a deficiency in training.

Thompson is now trying to achieve another means of justice through his complaint to the federal government. In it, he draws parallels between Williams’ conduct in his case and several others. Thompson also references sworn statements made by Williams in which he says he handled evidence in the case in the exact manner he was taught and the way he had done in some 100 additional homicide cases.

The Orleans Parish District Attorney’s office did not immediately respond to calls for comment on Thompson’s petition.

For his part, Williams defended his conduct in the Thompson case. “To make the record clear for the very last time, I never withheld any favorable evidence in either of John Thompson’s criminal trials that I prosecuted,” he said in a written statement. “Nearly twenty years ago, I testified numerous times on that issue while it was being litigated in State and Federal Court. I was completely cleared of any wrongdoing.”

Thompson and his attorneys remain unconvinced, and they said the Justice Department has agreed to meet with them.“Because this was Mr. Williams’ usual behavior and he prosecuted many other individuals, we can assume that many more individuals were affected by his wrongdoings,” Thompson’s complaint states. “We can further assume that some of Williams’ victims were not as lucky as Mr. Thompson — that some have not been freed from their wrongful incarceration … The federal government simply cannot and should not turn a blind eye to this prosecutor’s consistent violation of the constitutional rights.”

In 2013, ProPublica examined prosecutorial misconduct in New York City. We found more than two dozen instances in which judges concluded that city prosecutors had committed misconduct, and yet, as in Thompson’s case, the prosecutors were almost never punished. In fact, many prosecutors in our analysis had been promoted and received raises even after appellate courts excoriated them for failing to disclose evidence and committing other forms of misconduct.

Williams was promoted many times within the Orleans Parish District Attorney’s office before he left in 1990. Currently he works as a defense attorney in Gretna, Louisiana.

At a press conference announcing his Justice Department complaint, Thompson likened Williams’ misconduct to murder.

“The definition of murder is attempting to take someone’s life,” he said. “And if this isn’t someone attempting to take someone’s life, I don’t know what is.”