The state of Missouri is scheduled to execute Marcellus Williams on August 22 despite a lack of solid evidence used to secure his conviction and a new report from a DNA expert that his lawyers argue supports his claim to innocence.

“The death penalty is abhorrent in any circumstance, and as we have seen time and time again, the capital justice system is capable of error,” said Zeke Johnson, senior director of programs at Amnesty International USA. “The state of Missouri must not allow this execution to go forward, and must commute the sentences of all of those on death row. There is no acceptable way for the state to kill its prisoners.”

Williams was convicted of the 1998 murder of former St. Louis reporter Felicia Gayle by a jury consisting of 11 white jurors and one black juror. Williams is black and Gayle was white. There was no forensic evidence or eyewitness testimony linking him to the crime. The jury was not presented evidence of Williams’ background, which included severe abuse and mental disability.

Two experts retained by the appeal lawyers have concluded that DNA testing conducted in December 2016 on the murder weapon excludes Williams as the contributor of the male DNA found on the knife. The lawyers have just filed the latest expert report they have obtained on this with the Missouri Supreme Court in a bid to obtain a stay of execution.