On Super Bowl Sunday 2007, four-year-old Ella Bennett was killed in her bed in Abilene, Texas. The person responsible was her thirteen-year-old brother, Paris. He has said Ella wasn't his target. Their mother was.

Two years later in St. Martins, Missouri, nine-year-old Elizabeth Olten walked to a friend's house and never came home. Fifteen-year-old Alyssa Bustamante had dug a grave days earlier. She told investigators she wanted to know what killing felt like.

In this episode, we look at both cases side by side. We cover:

• How Paris Bennett set up the night he killed his sister, and the 911 call that followed
• Why intelligence and empathy are not the same thing
• What researchers mean by psychopathic traits, and why that label is so hard to apply to children
• Nature versus nurture and the developing teena ...