Two U.S. inmates face execution on Tuesday, including a Mississippi man whose lawyers called for a halt to the proceeding after federal authorities said last week they overstated the strength of a piece of evidence during trial.
The lethal injections of Willie Jerome Manning from Mississippi and Texas inmate Carroll Parr would be the 11th and 12th executions in the United States this year, according to the Death Penalty Information Center.
Manning was convicted of the 1992 murder of two college students, and Parr was convicted of killing a man during a 2003 robbery.
Texas has already executed four inmates this year; Mississippi has not executed any.
In the Mississippi case, the Federal Bureau of Investigation and U.S. Department of Justice said in letters last week to state officials that an FBI examiner had overstated conclusions about a hair found in Miller's car by suggesting that it came from an African American.
Manning, now 44, is black and the two victims, Mississippi State University students Tiffany Miller, 22, and Jon Steckler, 19, were white. The hair sample was the only physical evidence linking Manning to the crime scene.
"We have determined that the microscopic hair comparison analysis testimony or laboratory report presented in this case included statements that exceeded the limits of science and was, therefore, invalid," federal authorities said.
Manning's lawyers have asked the Mississippi Supreme Court to halt his lethal injection in light of the revelations.
Mississippi Attorney General Jim Hood accused Manning of waiting until the last minute to raise "this frivolous issue."
According to prosecutors, Manning crossed paths with Miller and Steckler when the couple unwittingly interrupted him burglarizing a car outside a fraternity house they were leaving in December 1992. Manning had a history of theft and other charges and had recently been paroled, prosecutors said.
Manning forced the couple into Miller's car, robbed them and shot them, prosecutors said. Their bodies were discovered on a rural road near the university campus in Starkville.
Manning was arrested after he tried to sell some items belonging to the victims.
In the Texas case, Parr was convicted of the 2003 murder of Joel Dominguez in Waco.
Parr, now 35, bought marijuana from Dominguez at a convenience store and then returned to the store with a friend to get his money back, according to an account of the case from the Texas attorney general's office. Parr and his friend, who were armed, forced Dominguez and another man to a fenced area near the store.
Parr pistol-whipped Dominguez, got his money back from him, then told his friend to "smoke 'em," the account said. Parr fatally shot Dominguez in the head, and Parr's friend shot the other man in the hand.
Parr already had a criminal record that included convictions for delivery of cocaine and evading arrest, and prosecutors presented evidence that he was involved in another murder in 2001.
The U.S. Supreme Court in January denied a request for Parr's case to be reviewed.