Marti Hill did not show up for work one day in September 2010, and her co-workers grew concerned. Police were summoned after Hill’s boss drove to her home and found her car still in the driveway. She was found by police, at the bottom of the basement steps, barely breathing and covered in blood....

On September 4, 2006, Kathy Wangler, wife of anesthesiologist Dr. Mark Wangler, died from carbon monoxide poisoning in their home in Lima, Ohio. Their thirty-year marriage had been falling apart; three years later, in 2009, investigators came to the conclusion that Dr. Wangler had murdered his...