Nebraska does forbid the execution of the mentally...

Nebraska does forbid the execution of the mentally retarded and juvenile offenders.
As a consequence of a 2002 law adopting the provisions made as a consequence of the Supreme Court ruling on the Ring v. Arizona case, sentencing can only be decided by a unanimous jury.
On August 4, 2001 the Supreme Court of Nebraska, where 3-judge panels generally decide death sentences, has ruled that such sentences are unconstitutional when determined with only a 2-1 majority. The state has life without parole.
A three-judge panel decides the sentence. An executive panel, which includes the Governor, has the power to grant clemency.