Missouri sentenced a man to death Tuesday despite objections from prosecutors who wanted to overturn his conviction and supported his claims of innocence.

Marcellus “Khaliifah” Williams, 55, was killed by lethal injection, ending a legal battle that drew widespread outrage after the office that originally handled the case suggested he had been wrongly convicted.

In an extraordinary move condemned by civil rights advocates and lawmakers across the US, Missouri’s Republican Attorney General Andrew Bailey went ahead with the execution, against the wishes of the St. Louis District Attorney’s Office.

Williams was convicted of the 1998 murder of Lisha Gayle, a social worker and former reporter for the St. Louis Post-Dispatch. He was accused of breaking into Gayle’s home, stabbing her to death and stealing some of her belongings.

However, there was no forensic evidence linking Williams to the murder weapon or the crime scene. In addition, local prosecutors vacated his conviction, while the victim’s family and several jurors also testified that they opposed his execution.

Williams, who served as an imam at his prison and devoted his time to poetry, saw his execution twice postponed at the last minute. He was days away from execution in January 2015 when the Missouri Supreme Court granted his attorneys more time for DNA testing. In August 2017, Eric Greitens, then the Republican governor, granted a stay just hours before the scheduled execution, citing DNA tests on the knife that found no trace of Williams’ DNA.

Greitens appointed a panel to investigate the matter, but when Mike Parson, the current Republican governor, took over, he disbanded the panel and insisted that the execution go ahead.

In January, Wesley Bell, the Democratic prosecutor in St. Louis who has championed criminal justice reform, filed a motion to overturn Williams’ conviction. Bell cited repeated DNA testing that showed Williams’ fingerprints were not on the knife.

“Ms. Gayle’s killer left behind considerable physical evidence. None of that physical evidence can be linked to Mr. Williams,” his office wrote, adding, “New evidence suggests that Mr. Williams is in fact innocent.” He also alleged that Williams’ defense counsel at the time was ineffective.

However, additional tests on the knife showed that employees of the district attorney’s office had mishandled the weapon after the killing — touching it without gloves before the trial, Bell’s office said. A forensic expert testified that the mishandling of the weapon made it impossible to determine whether Williams’ fingerprints could have been on the knife earlier.

In August, Williams and prosecutors reached a deal to halt his execution: He would plead no contest to first-degree murder in exchange for a new sentence of life in prison without the possibility of parole. His attorneys said the agreement was not an admission of guilt and was intended to preserve his life while he sought new evidence to prove his innocence. A judge signed the agreement, as did the victim’s family, but the attorney general challenged the deal and the state Supreme Court blocked it.

The latest efforts by both Williams’ attorneys and prosecutors in St. Louis in recent days have been unsuccessful. In a weekend plea, Bell’s office said there were “constitutional flaws” in Williams’ prosecution and pointed to recent testimony from the original prosecutor, who said he rejected a potential black juror because he looked like he could be Williams’ “brother.” The jury that convicted him consisted of 11 white members and one black member.

The governor also rejected Williams’ request for clemency on Monday, noting that the victim’s family and three jurors supported calls to overturn his death sentence. The U.S. Supreme Court on Tuesday rejected a final request to halt the execution.

The attorney general argued in court that the original prosecution denied there was a racial motive for removing black jurors and that there was nothing improper about touching the murder weapon without gloves at that time.

Bailey’s office has also suggested that other evidence points to Williams’ guilt, including testimony from a man who shared a cell with Williams and said he confessed, and testimony from a friend who claimed to have seen stolen items in Williams’ car. Williams’ attorneys, however, argued that both witnesses were unreliable, saying they had been convicted of crimes and were motivated to testify by a $10,000 reward offer.

Bailey and Parson declined to comment on their decision to ignore the wishes of the victim’s family, but they did point out that the courts repeatedly upheld Williams’ conviction during his years-long appeals process.

Jonathan Potts, one of Williams’ lawyers, told the Guardian on Monday that the case would create further distrust in criminal justice: “The only way to create public confidence in the justice system is for the system to be prepared to admit its own mistakes … The public here sees the justice system at its most dysfunctional.”

Michelle Smith, co-director of Missourians to Abolish the Death Penalty, said she considered Williams a mentor, in an interview before his execution: “He means so much to so many people. He’s a friend, a father, a grandfather, a son. He’s a teacher. He’s a spiritual advisor to so many other young men. His absence would be a great harm to so many people.”

Smith said she hoped his case would help the public understand that “the death penalty doesn’t work.”

“I know people who say, ‘We shouldn’t kill innocent people, but otherwise I believe in the death penalty.’ But if you believe in the system at all, that means you’re okay with innocent people being killed, because the system is not perfect. It’s going to kill innocent people.”

Robin Maher, executive director of the Death Penalty Information Center, said she was not aware of another case in which someone was executed after a sitting prosecutor objected and admitted to constitutional errors that undermined the conviction. Since 1973, at least 200 death row inmates have been exonerated, her group said.

Williams’ execution is one of five scheduled to take place in the U.S. in a week. South Carolina executed a man on Friday, days after the state’s key witness recanted his testimony.