Eric Robert was to be put to death by lethal injection at 10 p.m. Monday, the Sioux Falls (South Dakota) Argus-Leader reported.
Robert had his last meal -- Moose Tracks ice cream -- Saturday, his lawyer, Mark Kadi, said.
Robert requested the death penalty after he confessed to the April 12, 2011, murder of corrections officer Ronald "R.J." Johnson during an attempted escape from the South Dakota State Penitentiary.
Kadi said it was not likely that Robert would request a habeas corpus appeal that could halt his execution.
"He's been very calm," Kadi said. "I've seen him angry and stressed out, and that's not what he is right now."