Most US residents worry about leaving their home unprotected while they work or travel. And if they live in "bad" neighbourhoods where crime is frequent, they may even have trouble sleeping. Unfortunately, leaving fear is not that unusual today. Elderly people living alone and latch-key kids at home alone after school are vulnerable and less able to protect themselves. Fear may even drive people to keep guns in their home, introducing the risk of being injured or killed by your own weapon.