Police arrested two men Thursday morning in connection with Washington, D.C.-area sniper shootings. Someone claiming to be the sniper placed several phone calls to police earlier this week. How easy is it for cops to trace a phone call?
Contrary to what pulp screenwriters seem to believe, it's pretty darn easy nowadays. Tracing problems are a relic of manual switchboards, which required operators to physically connect circuits. In order to track down a caller's location, police needed 10-20 minutes to figure out the maze of circuits. This is where the cinematic stereotype of "Keep 'em talking" comes from—shorter calls could only be traced back part of the way, to a nearby switching station rather than the source phone.
Digital switches have sped up the process. Beginning in the mid-1980s, phone companies began using electronic switching systems, which can automatically identify any caller's number within a fraction of a second. Those numbers can then be correlated with information from an automatic location indicator to find the phone's address. There is no foolproof way to avoid tracing on an ESS network when making a direct-dial call. (And don't think for a second that hitting *67, which masks your number to Caller ID boxes, can foil a police trace; it only works against civilians.)
Some local phone companies allow users to trace calls through a feature called *57. Users hang up, wait 10 seconds, and then press *57. The caller's information is immediately forwarded to the phone company's computers, where it can later be accessed by the police. But the feature isn't available everywhere, and in some cases it won't trace calls made with calling cards or through operator assistance.
Mobile phones have proven harder to trace over recent years, but that is changing, too. The Federal Communications Commission has ordered that, by 2006, all cell-phone networks must feature location-tracking technology, ostensibly to assist 911 operators. As a result, many new mobiles now come equipped with chips that link them into the Global Positioning Satellite system. Triangulation using coordinates from adjacent cell-phone towers is another effective tracing technique.
Tracing a phone call is only half the investigative battle, of course. Few suspects, alas, are dumb enough to stay put after placing a taunting call to the cops.