The impending execution of a 55-year-old Missouri man – who maintains his innocence – is the latest in a series of cases that have brought the death penalty back into focus.

In 2001, Marcellus Williams was sentenced to death for the 1998 murder of social worker and former St. Louis Post-Dispatch reporter Felicia “Lisha” Gayle. Since his conviction, questions have been raised about how evidence was handled in the case and whether jury selection for his trial was fair.

Given these concerns and Williams’ continued claims that he did not kill Gayle, he and St. Louis District Attorney Wesley Bell asked the state to overturn his sentence. Although his execution had been postponed twice before, the Missouri governor and state Supreme Court refused again last week.

These decisions and the great uncertainty surrounding Williams’ case have cast a new light on the death penalty and many of the issues surrounding it. Unless the U.S. Supreme Court makes a decision, Williams is scheduled to be executed by lethal injection on Tuesday evening.

Williams was convicted of Gayle’s murder based on the testimony of two witnesses, including his then-girlfriend, who said she saw the victim’s purse and laptop in his car. Williams was in prison at the time of his conviction in the Gayle case, and his then-cellmate Henry Cole also claimed that Williams admitted to the murder.

According to the Washington Post, Williams’ lawyer argues that both witnesses had other motives for singling him out, including “bounties and agreeing to shorter prison sentences in their own criminal cases.”

As USA Today notes, there was no forensic evidence linking Williams to the crime, and his DNA was not found on the murder weapon – a knife.

Since his conviction, Williams’ attorney has called for a more thorough investigation of the DNA found on the knife and a review of racial bias in jury selection. Gayle’s family has also advocated for clemency and the possibility of a life sentence without parole.

Previously, Williams’ attorney convinced former Missouri Governor Eric Greitens that new testing of DNA evidence, including that of another man, had the potential to exonerate him, prompting Greitens to grant a stay of execution in 2017 and convene a panel to study the evidence.

In the meantime, however, the lawyers learned that the knife contained fingerprints and DNA from a prosecutor who had touched the murder weapon without gloves, thus contaminating the evidence.

Williams’ allies also argued that racial bias occurred in his trial after a former prosecutor claimed he excluded a black juror because of his resemblance to Williams.

Williams’ lawyers have asked the U.S. Supreme Court to grant a stay of execution based on this evidence of bias, but it is not yet clear whether the court will do so.

The Missouri Supreme Court had rejected this, with Judge Zel Fischer arguing that there was “no credible evidence of actual innocence or proof of a constitutional error that could undermine confidence in the original verdict.”

The death penalty has been used less and less in recent years, as concerns have grown about its deterrent effect and humanity, as well as racial disparities in death sentences. According to a 2016 study in Washington state, black defendants are four times more likely to be sentenced to death than non-black defendants under similar circumstances.

Although 27 states still allow the death penalty, 14 of them have not carried out any executions in the past decade, according to CNN. The number of executions has also declined since 1999, when a new high of nearly 100 was reached. In 2023, 24 people were executed in five states; 24 executions are currently expected this year.

Among the fears that executions provoke is the fear that these sentences threaten innocent people. Williams’ team firmly believes that his case is an example of this problem.

“Missouri is on the verge of executing an innocent man, an outcome that calls into question the legitimacy of the entire criminal justice system,” Tricia Bushnell, an attorney with the Midwest Innocence Project who is representing Williams, said in a statement.

According to the Death Penalty Information Center, at least 200 people wrongfully sentenced to death have been rehabilitated since 1973. And according to a 2014 study, about 4 percent of those sentenced to death are innocent.