IN DECEMBER 1997, a fourteen-year-old boy shot and killed three teenagers and wounded five others at Heath High School in West Paducah, Kentucky. In April 1999, two teenage students in Littleton, Colorado, planned to blow up Columbine High School after a shooting spree that took fifteen lives, including their own. During a three-week rampage in October 2002, a seventeen-year-old sniper and his older mentor terrorized the Washington, D.C., area, killing ten people and wounding three.

Some people believe these horrific acts occurred because violent media—movies, television shows, music, or video games—created these young killers. Psychologists and media experts theorized that Paducah resident Michael Carneal was inspired to emulate a scene from the 1995 movie The Basketball Diaries. The fascination of Columbine killers Eric Harris and Dylan Klebold with "shock rock" musician Marilyn Manson and the video game Doom is believed to have provoked their deadly rampage. Lawyers...