The case of Darren Deon Vann, who police say confessed to murdering as many as seven women in northwest Indiana over the past couple of years, is just the latest example of a kind of crime spree that has become all too familiar. At a time when television crime dramas like "CSI," "Criminal Minds," and "Law and Order" record high ratings with lurid plot lines about repeat killers, it is easy to come away believing that serial killings are as prevalent as they have ever been.