Missouri has executed a man convicted decades ago in the stabbing murder of an elderly Ozark woman, marking the country’s first capital punishment since the coronavirus pandemic began.

Walter Barton, 64, received a death sentence for the 1991 slaying of Gladys Kuehler, an 81-year-old who owned a mobile home park in Ozark.

Over a span of almost three decades, the case has gone through appeals, mistrials and two overturned convictions. But the end arrived after the Supreme Court denied a stay of execution earlier Tuesday, and Gov. Mike Parson declined to grant clemency.

Barton was with Kuehler’s granddaughter and a neighbor the night of Oct. 9, 1991, when they discovered the victim’s body in her bedroom, The Associated Press reported. She had been beaten, sexually assaulted and stabbed more than 50 times.

FILE - This Feb. 18, 2014, file photo provided by Missouri Department of Corrections, shows death row inmate Walter Barton, convicted of killing an 81-year-old mobile home park manager in 1991. The pause in U.S. executions during the coronavirus pandemic likely will end Tuesday, May 19, 2020, with the scheduled lethal injection of Barton. Republican Missouri Gov. Mike Parson said Monday, May 18, 2020, that he had not heard anything to make him reconsider the execution, which he said would “move forward as scheduled.” (Missouri Department of Corrections via AP, File)

Police found three small bloodstains on Barton’s clothing, but he said that it got there when he pulled the granddaughter away from the body.

She initially confirmed that version of events -- only to testify later that Barton never actually entered the bedroom.

During the trial, a blood spatter expert said the small stains likely came from the “impact” of the knife.

But more recent court filings cited a different examination, which concluded the killer would have had much more blood on his clothes, according to Barton's attorney, Fred Duchardt Jr.

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Duchardt said three jurors from the trial recently signed affidavits calling the new development "compelling" and saying it would have affected their deliberations. The jury foreman said that based on the new evidence, he would have felt “uncomfortable” recommending Barton for the death penalty.

Authorities have postponed scheduled executions as the coronavirus outbreak complicated last-minute appeals and clemency requests and made obtaining records or conducting interviews difficult, according to attorneys for death row inmates across the country.

Barton’s execution is the first in the U.S. since Nathaniel Woods Jr. was put to death in Alabama in early March for his role in the 2004 killings of three police officers.

It was conducted in a prison with no confirmed cases of the coronavirus. Everyone entering the facility underwent a temperature screening and was provided with a face mask if they showed up without one. Witnesses to the execution were divided between three rooms, and social distancing was maintained, although some individuals reportedly chose not to wear masks.

Fox News’ Shannon Bream, Bill Mears and The Associated Press contributed to this report.