Killen, 81, was convicted last year of manslaughter in the slayings of James Chaney, Michael Schwerner and Andrew Goodman.
He was sentenced to 60 years in prison but has been in poor in health, and his attorneys argued that the former sawmill operator and preacher should be allowed out of prison for health reasons during his appeals.
They said Killen couldn't attend the hearing Friday before Neshoba County Circuit Judge Marcus Gordon because he has an intravenous drip in his arm and that would have required an ambulance to transport him to the courthouse. The state Department of Corrections had said it would not provide an ambulance for the trip.
Killen was the only person to face state charges in the deaths, which were dramatized in the 1988 movie "Mississippi Burning."
He had been tried along with several other men in 1967 on federal charges of violating the victims' civil rights, but the jury deadlocked. Seven others were convicted, but none served more than six years in prison.