From 20 to 300 in three killings

Allen Breed reports "the number of serial killers out there is elusive."

At first, this can seem like an obvious statement, almost laughable in its simplicity, but there are so many schools of thought behind the estimated number of serial killers, any black and white statement would seem too bold.

Jack Levin, who studies violence at Boston's Northeastern University, estimates conservatively that there are about 20 serial killers operating nationwide, accounting for about 200 victims a year. Ann Rule, a true-crime author and serial killer expert from Seattle, figures there are about 300 such predators lurking "just below our level of awareness."

"In the past we have had people here on our staff that have tried to make educated - or uneducated, guesses," says FBI spokesman Ken Gross. He said the FBI's headquarters offices were working with state and local officials on 16 cases they believe are connected to serial killers, but there may be others not involving the headquarters.

Back when he coined the phrase "serial killer," former FBI profiler Robert Ressler could safely say that most of his prey were single, white, unemployed males. And it seemed the United States had the market cornered.

Now we know there are serial killers everywhere, from America to Australia. America's proclivity towards violence, the expanse of the land itself and the ease with which weapons can be procured could arguably be said to explain the higher number in this country. Studies on the environment capable of producing a serial killers, no matter how extensive, can never be definitive. These aren't cooperative subjects giving will testimony. Even killers like Henry Lee Lucas (the only murderer George W. Bush saved from the death penalty), despite an apparent talkativeness, are more than capable of outright lies.

These killers are, and will remain, elusive to those that try to understand them and those that try to understand them.

When people question why serial killers go so long without being caught, Ressler is piqued.

"When you get a person that is a ghost, who is operating in an invisible status, it can take a long time."