Ask a criminologist about a really offbeat crime, and there's a good chance he can tell you the year. Tylenol bottles laced with poison on supermarket shelves? 1982. Syringes planted in Pepsi cans? 1993. Letters purportedly containing deadly anthrax? 1998. Reason: those are the years when a wave of similar crimes suddenly began appearing across the country.
Ever since the Columbine High School killings, the copycat syndrome has been working overtime. In recent weeks hundreds of schools have been hit with threats of Columbine-like violence. In Wilkes-Barre, Pa., junior and senior high school classes were canceled after a bomb threat was...