Here's the key quote from the judge who wrote the court's 6-1 majority opinion:
"We recognize the temptation to make the prisoner suffer, just as the prisoner made an innocent victim suffer. But it is the hallmark of a civilized society that we punish cruelty without practicing it. Condemend prisoners must not be tortured to death, regardless of their crimes. And the evidence clearly proves that unconsciousness and death are not instantaneous for many condemned prisoners. These prisoners will, when electrocuted, consciously suffer the torture that high voltage electric current inflicts on the human body. The evidence shows that electrocution inflicts intense pain and agonizing suffering. Therefore, electrocution as a method of execution is cruel and unusual punishment in violation of the Nebraska Constitution."