Serial Killer

They murder without remorse and torture in a cruel way, killing not just once, but again and again: serial killers. Thanks to Hollywood, Hannibal Lecter is considered the epitome of a serial killer. In real life, too, the killers regularly make the front pages of the gazettes. But what drives these people to evil? Is there such a thing as a killer gene? Are these people born as murderers or only through socialization to them?