Forget humane.
Was he humane to his victim? She was buried alive.
The criminal should have the same experience as the victim.
A central line insertion (so the vein won't fail).
Paralytics (no sedation necessary). That might give that buried alive feeling.
Followed by a bolus of potassium.
Of course, all performed by the proper authorities.
The thought of that cocktail might be a deterrent to crime.
See, there is humanity if the punishment is so frightening it prevents crime.
Just sayin.