As the trials get under way for the two men accused in the 10 Washington-area sniper deaths last October, questions are being raised about our understanding of serial killers, and how many there are. Most research has focused on those who kill for sexual gratification. Far less is known about "spree killers," as some have described the Washington snipers. Since the 1970s, the FBI has touted its criminal-profiling method for finding serial killers. But critics say profiles have little science behind them and can lead investigators astray. Modern DNA technology holds out promise for linking serial killers to crime scenes - and even stopping killers before they strike again. But civil rights lawyers are challenging the widespread sharing of suspects' DNA by law enforcement agencies as unconstitutional.

Sarah Glazer specializes in health, education and social-policy issues. Her articles have appeared in The Washington Post, Glamour, The Public Interest and Gender and Work, a book of essays. Glazer covered energy legislation for the Environmental and Energy Study Conference and reported for United Press International. She holds a BA in American history from the University of Chicago.