In April 1996, an infant was thrown out of his bassinet and beaten and kicked into a coma. The tragic fact that this baby became permanently brain damaged was overshadowed by the horrifying discovery that the perpetrator of the vicious act was a six-year-old boy. This incident greatly perplexed prosecutors, defense attorneys, and judges faced with trying such a young suspect. It also heightened the public’s growing fear that violent crime is increasing at the hands of younger and more vicious predators.

Many commentators point to such troubling incidents as proof that youth violence is becoming a serious problem. For instance, the Council on Crime in America, a bipartisan commission on violent crime, has warned of a “coming storm of juvenile crime.” Pointing to demographic trends that indicate that the number of fourteen- to seventeen-year-old males will increase...