Fridge Logic: At the end of the movie, Ruben has still essentially gotten away with murder.
Double jeopardy only means that he can't be tried again after a legitimate "not guilty" verdict; the verdict came as a result of jury tampering, and once this comes to light, it's likely a mistrial will be declared. Even if the verdict is upheld, it's likely he'll find his stay in prison greatly extended once his involvement in Nash's jailbreak comes to light.
"Funny Aneurysm" Moment: Before Ernest is put on the electric chair, he's asked if he wants a blindfold or a smoke. He declines saying "Cigarettes will kill you." Jim Varney succumbed to lung cancer from a lifetime of heavy smoking in 2000.