Murder is murder, Dharma. Any DA that tried to paint Couey's act as 'manslaughter' or any lesser charge doesn't deserve the job.
Had Blake's wife been snatched from her bed, tortured, and buried in a close proximity to Blake's house, I'd agree with you. In reality, she was killed in a public place, after having lived a life practically daring people to do just what was perpetrated. Testamony of her acts showed that any number of people had a motive and ability to kill her.
There's no comparison, imho. If this guy's lawyer, as you say, is an underpaid civil servant with few resources, then won't he be MORE apt to suggest a plea, instead of fighting a battle he is ill-equipped to win?