To police, it is the witness that never lies, never forgets, never changes its story. And while its vision often is blurred, it sees much that others miss.
The electronic eye of the surveillance camera has become a treasured tool of criminal investigators. As the gaze of security cams permeates stores, lobbies, sidewalks, schools, parks and parking lots, so have its date-stamped images risen on a detective's checklist.
"Video gives you definitive answers; it's not left to subjective memory or someone's recollection or someone's lies," said Camden County Prosecutor Vincent Sarubbi. "You see it in black and white, and you know whether or not it happened."
An estimated 1.3 million surveillance cameras are operating in the United States, said Joe Freeman, head of J.P. Freeman Co. Inc., a leading consultant to the security industry. That's up by as much as 30 percent over the last five years, he said, with office buildings and banks being the primary users.
Philadelphia police are hoping for a tech-assisted break in the baffling predawn slaying of a hospital worker last week in Center City.
Cameras mounted on a federal building yielded grainy images of a man shooting Patricia McDermott at 4:45 a.m. May 17 on a Ninth Street sidewalk. Police have publicized those images while scouring nearby security cameras for more glimpses of suspects and witnesses.
"It is one of the most important things to law enforcement right now," said Bucks County District Attorney Diane E. Gibbons. "Where before we would have to rely solely on witnesses' descriptions of a suspect, now every time there is a major crime, one of the first things we do is to look for any and all videotapes in that area."
Last month, Gibbons' detectives used surveillance photos to solve a slaying just as vexing as the McDermott shooting.
William L. Berkeyheiser, an affable retired health-care executive, had been gunned down inexplicably on Easter at the door of his Upper Makefield home. A day later, investigators learned that shortly before the shooting, a man had stopped at a nearby convenience store and asked for directions to Berkeyheiser's street.
The man's image was captured by a store surveillance camera and publicized. A flood of tips ensued, one leading to Stanford Douglas, a onetime coworker who confessed to shooting Berkeyheiser over a racial joke Berkeyheiser allegedly had told in 1997.
"We would not have solved the case without that tape," Gibbons said.
Such opportunities will only expand as the post-9/11 demand for security equipment grows. Prosecutors in the Philadelphia region and other urban areas already have abundant tales of cases solved or aided through surveillance photos or videos.
In 1999, the man who fatally stabbed Philadelphia Daily News columnist Russell Byers outside a Chestnut Hill Wawa store was identified from surveillance tapes.
In 2000, exotic dancer Rachel Siani was allegedly dumped, while unconscious, from a Delaware River bridge in Burlington County. A bridge camera captured an image of a woman's body lying in the bed of the pickup truck of her accused killer.
And in Montgomery County, a man accused of raping and fatally stabbing 19-year-old Anna Nicole Fowler last year in a King of Prussia motel faces a double video whammy. Cameras captured him checking into the motel before the slaying, and using the victim's ATM card afterward.
There are prominent national examples as well.
A security camera image of a Ryder truck just before the Oklahoma City bombing helped lead investigators to Timothy McVeigh. In Sarasota, Fla., a security camera captured the haunting image of 11-year-old Carlie Brucia being abducted by her killer - an image that helped lead to his arrest.
Less often, but just as effectively, security video has helped clear suspects.
In 1999, an owner of a Willingboro music store fatally shot his business partner. No charges were filed after a grand jury was shown a store video confirming that the shooting was accidental.
"It was very tragic and just bone-chilling to see," recalled Willingboro Police Capt. Donna Dimitri.
Yet there is also frustration with the uneven quality of the images. And privacy advocates fret over the growing use of cameras in public places.
"Videotapes are evidence, and once they are brought into creation, it is natural for police to seek out evidence in investigating a crime," said Jay Stanley, a privacy coordinator for the American Civil Liberties Union in Washington. "The question is, do we want to create a society in which our every move becomes potential evidence?"
While there have been no systematic measures of how many security cameras are out there, "it's quite clear that they have expanded dramatically," Stanley said.
Industry experts and privacy groups agree that there has been no public backlash against surveillance cameras.
Most people appreciate the added layer of security, said David Smith, vice president of marketing for Pelco, one of the world's largest manufacturers of video security equipment. Plus, there have been relatively few abuses of the technology - such as placing hidden cameras in public restrooms, Smith said.
"Only one-one-hundredth of 1 percent of all security videos are ever watched," Smith said. "What it is used for almost all the time is forensic investigation, for reconstructing something after it has occurred."
The ACLU's Stanley argues that as people become more aware of the extra eyes upon them, concerns will grow. Stanley is especially concerned about efforts in some cities, including Philadelphia, to place police-operated cameras in suspected high-crime areas.
"It is a different thing than having a police officer sitting on a street corner," he said. "If you had one following you around constantly and writing down your every move, that would be unnerving to you."
As cameras have become cheaper and more numerous, the quality of their images has not kept up, police complain. The biggest improvement, they say, is digital technology that enables businesses to store images longer, making them more available to investigators.
But no amount of lab enhancements will turn a grainy, nighttime image into a recognizable face, experts say.
"There's no real Star Wars magic that will turn a fuzzy picture into a crystal-clear picture," Pelco's Smith says. "If you expect to get a conviction on a picture alone... you've got to be talking about shooting a very confined area."
Many outdoor cameras are designed to sweep a much larger area. That has been the problem with the images of last week's Center City shooting, Philadelphia homicide Capt. Richard Ross said; the suspect's image is too grainy for identification.
"We had some of the best enhancers from NFL Films and the FBI take a look at it, and there was nothing more they could do," Ross said. The film "at least gave us a picture of what happened, and we are thankful for that."