Condemned murderer Mark Hopkinson's fate remained uncertain Monday as the attorney general's office prepared to ask the 10th U.S. Circuit Court of Appeals to vacate a stay of execution granted the killer Sunday.

The justices, in Cheyenne for other business, agreed to hear the state's arguments at 10:40 a.m. Monday, said Bob Hoecker, clerk of court for the appellate court."There's no set time, so they will hear arguments for what seems reasonable," he said. "They could rule from the bench, but customarily they adjourn and confer before they issue any ruling."

Hoecker said if so convinced, the justices could vacate the stay granted Hopkinson on Sunday by U.S. District Judge Richard P. Matsch and thus clear the way for the execution to take place early Tuesday as scheduled.

In granting the stay Matsch agreed with Public Defender Leonard Munker that the jury that sentenced Hopkinson to die might have received improper instructions in reaching that verdict.

Hopkinson has been sentenced to death on his conviction of ordering the death of Jeffrey Lynn Green in 1979.

Karen Byrne, the senior assistant attorney general handling the state's side in the case, said Sunday she had expected the latest appeal filed in an effort to halt the execution to result in a hearing before the appeals court.

"These stays and requests to vacate stays, as I understand, are very common in death penalty cases, judging from the experience of other states," she said. "We were expecting and the district court judge was expecting (the) side that did not prevail to file an appeal to the 10th Circuit Court."

Matsch's ruling on Sunday came after three hours of arguments from the state and Hopkinson's public defenders.

In issuing the stay, Matsch said there is a possibility that the death penalty decision "was made under an erroneous view of the law."

At issue was whether the 1979 sentence was affected when the judge instructed the jurors they must reach their verdict unanimously.

Arguments on Sunday centered on whether the jurors believed that each of their decisions on aggravating circumstances, mitigating factors and the ultimate sentence had to be unanimous.

"At least one juror - and there is no way to know how many - believed there was no evidence to show Mark Hopkinson ordered the torture of Jeff Green," Matsch said.

However, Matsch did not dismiss the final issue, which questions testimony provided by Todd Hall in 1981.

Martin McClain, a former public defender who has returned to Wyoming to help Munker with the latest round of appeals, asked for a hearing to determine if Hall is a material witness who can provide information to clear Hopkinson.

Hall's request for immunity in exchange for information is currently before the Wyoming Supreme Court.