Rhonda Belle Martin, Serial Killer

Rhonda Belle Martin was a waitress living a hard scrabble life in Montgomery, Alabama. She routinely poisoned her husbands, even going so far as to marry her former son-in-law, and leaving him as a paraplegic. It was his illness that led police to investigate the odd deaths that occurred around Rhonda...and they eventually brought a confession out of her as she would admit to poisoning two previous husbands, three of her children and her own mother for starters.
She was tried and sentenced to the electric hair. Before she was strapped in, Rhonda was asked if she had anything to say. She shook her head and they flipped the switch. But what possessed Rhonda Belle to poison everyone around her? Financial motive? Or was it something more evil at work?