ST. LOUIS — Lawyers for a condemned Missouri inmate warn that the state is preparing to execute a potentially innocent man.

Marcellus Williams, 48, is scheduled to die Tuesday at the state prison in Bonne Terre for stabbing to death former St. Louis Post-Dispatch reporter Lisha Gayle during a 1998 robbery at her home in the suburb of University City. It would be the state’s second execution of 2017.

Williams’s attorneys have appealed to the Supreme Court, seeking a new hearing or the commutation of his sentence to life in prison.

They’ve also asked Governor Eric Greitens for clemency. A spokesman for Greitens did not immediately reply to a message seeking comment.

Attorney Kent Gipson contends that DNA testing conducted in December using techniques that were not available at the time of the slaying showed DNA found on the knife matches an unknown man, but not Williams.

He also cited previous DNA testing of hairs found from Gayle’s shirt and fingernails that also excluded Williams, and said footprints at the scene did not match Williams.

The new evidence ‘‘means in our mind the actual killer is not him,’’ Gipson said.

Loree Anne Paradise, a spokeswoman for Attorney General Josh Hawley, said the office remains confident that Williams is guilty based on other evidence in the case.

ASSOCIATED PRESS