The court upheld a lower court decision that Rita Bixby, 74, could not face the death penalty in the officers' deaths because she had been charged with accessory to murder, not murder itself. Authorities have said she knew her son was planning to kill officers who set foot on the family's land. Her trial date has not been set.
"A possible sentence of death applies only when one is convicted of or has pled guilty to the crime of murder," Monday's high court ruling said.
"The statute does not provide any other crimes for which a defendant may be eligible for the death penalty."
Chief Justice Jean Toal disagreed, writing in a dissenting opinion that "a charge of accessory before the fact to murder implicates the death penalty under South Carolina law."
In February, Steven Bixby, 39, was sentenced to death for the shooting deaths of two Abbeville County law enforcement agents. Prosecutors said the officers were killed over a 20-foot patch of land the state wanted to take for a highway project.
County sheriff's Sgt. Danny Wilson and state Constable Donnie Ouzts died in the Dec. 8, 2003, shootings at the Bixby home.
Steven Bixby's 77-year-old father, Arthur, has also been charged with murder and is awaiting trial.