Internet expert : Craigslist slaying suspect left a trail of clues behind in cyberspace . Philip Markoff says he used a tracer program on e-mail sent to slaying victim . BOSTON investigators even used a American Express search to help track down suspect . `` As one of the law enforcement people told me , if you can see it , they can see it , '' Mark Rasch , a medical student , pleaded not guilty in death of Mark Rasch .
Internet expert : Craigslist slaying suspect left a trail of clues behind in cyberspace . Philip Markoff says he used a tracer program on e-mail sent to slaying victim . BOSTON investigators even used a American Express search to help track down suspect . Mark Rasch , a medical student , pleaded not guilty in death of Mark Rasch .