Susan

At around 8 p.m. Susan put her barefooted sons in the car, strapped them in their car seats and began driving around. In her confession she stated that she wanted to die and was headed to her mother's house, but decided against it. Instead she drove to John D. Long Lake and drove onto a ramp, got out of the car, put the car in drive, released the brake and watched as her car, with her children sleeping in the back seat, plunged into the lake. The car drifted out a ways then slowly sank.

Susan Smith ran to a nearby home and hysterically knocked on the door. She told the homeowners, Shirley and Rick McCloud, that an black man had taken her car and her two boys. She described how she had stopped at a red light at Monarch Mills, when a man with a gun jumped into her car and told her to drive. She drove around some, and then he told her to stop and get out of the car. At that point he told her he wouldn't hurt the kids and then drove off with the boys who she could hear were crying out for her.  For nine days Susan Smith stuck the story of being abducted. 

http://crime.about.com/od/murder/a/susan_smith.htm