The effect of violence on violence.

This story on Planet Xbox 360 addresses the question of whether violent games have a causal relationship to violent acts.

"Unfortunately, these men and their victims would never have had a chance to play the latest violent games.  The crimes took place in 1991, a year before the first Mortal Kombat ever hit arcades, and seven years before the clumsy top-view Grand Theft Auto.  These are men, like millions before them, who did harm to their fellow man because of something about them and their circumstances that entertainment could never have extinguished or encouraged. "