Lancaster County District Court Judge Earl J. Witthoff and Douglas County District Court Judge J. Michael Coffey will sit with Madison County District Court Judge Patrick Rogers, who presided over Sandoval's trial.
A Hall County jury found Sandoval guilty of five first-degree murder charges for his part in the U.S. Bank murders in Norfolk on Sept. 26, 2002.
Nebraska Supreme Court Chief Justice John Hendry appointed the judges this month.
A sentencing date has yet to be set.
Defense attorneys for Sandoval and his co-defendant, Erick Vela, will challenge the state's sole method of execution, the electric chair, as unconstitutional.
A hearing on that issue is set for Jan. 29.