With those thousands of cameras, the odds are good that some image of the Washington sniper has been caught on videotape, reports CBS News Correspondent Bob Orr.
Dorothy Stout, a forensic video examiner, said the challenge is to sort through countless images to identify the anonymous gunman. "That individual has been captured by a video security system at some point in time. Probably more than once," she told Orr.
Investigators are comparing pictures from each crime scene, looking for a common vehicle, face or even shoes.
"We can look at multiple incidents and say, you know what, we're seeing the same individual with a red sweatshirt at this scene and at this scene and at this scene," Stout said.
And while no witness has seen the gunman, it is possible video technicians could pull an image out of the shadows using computer enhancements.
There are also cameras in the sky. Blackhawk helicopters, normally used to spot drug runners, are spying on commuter traffic. Officials are also using an army plane that monitored troop movements in Bosnia. It's capable of spotting a license plate fifteen miles away.
"If they were just looking for a white van, the camera would be able to lock onto that vehicle and track it out in the suburbs even if it was flying over downtown," said John Pike a security consultant.
And there is an unmarked spy plane in the sky. It's not taking pictures, but rather eavesdropping -- listening in on cell phones and radios for any conversations that could lead to the sniper(s).
But the high-tech hunt for the shooter can only take investigators so far. The desperate need for physical evidence also demands tedious low-tech work on the ground.
Police have been knee-deep in garbage looking for receipts, notes, maps -- anything that may have been left by the gunman.
In Richmond, investigators hauled away a pay phone used by the sniper. They've checked gun shops for records and searched crime scenes for tire tracks, fingerprints and fibers.
"The problem in all forensic science right now is going from the physical evidence to trying to pinpoint a suspect, and that's the really difficult part," said Walter Rowe, a forensic scientist at George Washington University.
Three weeks into the shootings, police still can't be certain if they're looking for a lone sniper or something more.