An armed robber burst into a Northeast Washington market, scuffled with the cashier, and then shot him and the clerk’s father, who also owned the store. The killer sped off in a silver Pontiac, but a witness was able to write down the license plate number.

Police figured out the name of the suspect very quickly. But locating and arresting him took a little-known investigative tool: a vast system that tracks the comings and goings of anyone driving around the District.

Scores of cameras across the city capture 1,800 images a minute and download the information into a rapidly expanding archive that can pinpoint people’s movements all over town.

Police entered the suspect’s license plate number into that database and learned that the Pontiac was on a street in Southeast. Police soon arrested Christian Taylor, who had been staying at a friend’s home, and charged him with two counts of first-degree murder. His trial is set for January.

More than 250 cameras in the District and its suburbs scan license plates in real time, helping police pinpoint stolen cars and fleeing killers. But the program quietly has expanded beyond what anyone had imagined even a few years ago.

With virtually no public debate, police agencies have begun storing the information from the cameras, building databases that document the travels of millions of vehicles.

Nowhere is that more prevalent than in the District, which has more than one plate-reader per square mile, the highest concentration in the nation. Police in the Washington suburbs have dozens of them as well, and local agencies plan to add many more in coming months, creating a comprehensive dragnet that will include all the approaches into the District.

“It never stops,” said Capt. Kevin Reardon, who runs Arlington County’s plate reader program. “It just gobbles up tag information. One of the big questions is, what do we do with the information?”

Police departments are grappling with how long to store the information and how to balance privacy concerns against the value the data provide to investigators. The data are kept for three years in the District, two years in Alexandria, a year in Prince George’s County and a Maryland state database, and about a month in many other suburban areas.

“That’s quite a large database of innocent people’s comings and goings,” said Jay Stanley, senior policy analyst for the American Civil Liberties Union’s technology and liberty program. “The government has no business collecting that kind of information on people without a warrant.”

But police say the tag readers can give them a critical jump on a child abductor, information about when a vehicle left — or entered — a crime scene, and the ability to quickly identify a suspected terrorist’s vehicle as it speeds down the highway, perhaps to an intended target.

Having the technology during the Washington area sniper shootings in 2002 might have stopped the attacks sooner, detectives said, because police could have checked whether any particular car was showing up at each of the shooting sites.

“It’s a perfect example of how they’d be useful,” said Lt. T.J. Rogers, who is responsible for the 26 tag readers maintained by the Fairfax County police. “We see a lot of potential in it.”

The plate readers are different from red-light or speed cameras, which issue traffic tickets and are tools for deterrence and enforcement. The readers are an investigative tool, capturing a picture of every license plate that passes by and instantly analyzing them against a database filled with cars wanted by police.

Police can also plug any license plate number into the database and, as long as it passed a camera, determine where that vehicle has been and when. Detectives also can enter a be-on-the-lookout into the database, and the moment that license plate passes a detector, they get an alert.

It’s that precision and the growing ubiquity of the technology that has libertarians worried. In Northern Virginia recently, a man reported his wife missing, prompting police to enter her plate number into the system.

They got a hit at an apartment complex, and when they got there, officers spotted her car and a note on her windshield that said, in essence, “Don’t tow, I’m visiting apartment 3C.” Officers knocked on the door of that apartment, and she came out of the bedroom. They advised her to call her husband.

A new tool in the arsenal

Even though they are relatively new, the tag readers, which cost about $20,000 each, are now as widely used as other high-tech tools police employ to prevent and solve crimes, including surveillance cameras, gunshot recognition sensors and mobile finger­print scanners.

License plate readers can capture numbers across four lanes of traffic on cars zooming up to 150 mph.

“The new technology makes our job a lot easier and the bad guys’ job a lot harder,” said D.C. Police Chief Cathy Lanier.

The technology first was used by the postal service to sort letters. Units consist of two cameras — one that snaps digital photographs and another that uses an optical infrared sensor to decipher the numbers and letters. The camera captures a color image of the vehicle while the sensor “reads” the license plate and transfers the data to a computer.

When stored over time, the collected data can be used instantaneously or can help with complex analysis, such as whether a car appears to have been followed by another car or if cars are traveling in a convoy.

Police also have begun using them as a tool to prevent crime. By positioning them in nightclub parking lots, for example, police can collect information about who is there. If members of rival gangs appear at a club, police can send patrol cars there to squelch any flare-ups before they turn violent. After a crime, police can gather a list of potential witnesses in seconds.

“It’s such a valuable tool, it’s hard not to jump on it and explore all the things it can do for law enforcement,” said Kevin Davis, assistant chief of police in Prince George’s County.

The readers have been used across the country for several years, but the program is far more sophisticated in the Washington region. The District has 73 readers; 38 of them sit stationary and the rest are attached to police cars. D.C. officials say every police car will have one some day.

The District’s license plate cameras gather more than a million data points a month, and officers make an average of an arrest a day directly from the plate readers, said Tom Wilkins, executive director of the D.C. police department’s intelligence fusion division, which oversees the plate reader program. Between June and September, police found 51 stolen cars using the technology.

Police do not publicly disclose the locations of the readers. And while D.C. law requires that the footage on crime surveillance cameras be deleted after 10 days unless there’s an investigative reason to keep it, there are no laws governing how or when Washington area police can use the tag reader technology. The only rule is that it be used for law enforcement purposes.

“That’s typical with any emerging technology,” Wilkins said. “Even though it’s a tool we’ve had for five years, as it becomes more apparent and widely used and more relied upon, people will begin to scrutinize it.”

Legal concerns

Such scrutiny is happening now at the U.S. Supreme Court with a related technology: GPS surveillance. At issue is whether police can track an individual vehicle with an attached GPS device.

Orin Kerr, a law professor at George Washington University who has been closely watching the Supreme Court case, said the license plate technology probably would pass constitutional muster because there is no reasonable expectation of privacy on public streets.

But, Kerr said, the technology’s silent expansion has allowed the government to know things it couldn’t possibly know before and that the use of such massive amounts of data needs safeguards.

“It’s big brother, and the question is, is it big brother we want, or big brother that we don’t want?” Kerr said. “This technology could be used for good and it could be used for bad. I think we need a conversation about whether and how this technology is used. Who gets the information and when? How long before the information is deleted? All those questions need scrutiny.”

Should someone access the database for something other than a criminal investigation, they could track people doing legal but private things. Having a comprehensive database could mean government access to information about who attended a political event, visited a medical clinic, or went to Alcoholics Anonymous or Planned Parenthood.

Maryland and Virginia police departments are expanding their tag reader programs and by the end of the year expect to have every major entry and exit point to the District covered.

“We’re putting fixed sites up in the capital area,” said Sgt. Julio Valcarcel, who runs the Maryland State Police’s program, which now has 19 mobile units and one fixed unit along a major highway, capturing roughly 27 million reads per year. “Several sites are going online over the winter.”

Some jurisdictions store the information in a large networked database; others retain it only in the memory of each individual reader’s computer, then delete it after several weeks as new data overwrite it.

A George Mason University study last year found that 37 percent of large police agencies in the United States now use license plate reader technology and that a significant number of other agencies planned to have it by the end of 2011. But the survey found that fewer than 30 percent of the agencies using the tool had researched any legal implications.

There also has been scant legal precedent. In Takoma Park, police have two tag readers that they have been using for two years. Police Chief Ronald A. Ricucci said he was amazed at how quickly the units could find stolen cars. When his department first got them, he looked around at other departments to see what kind of rules and regulations they had.

“There wasn’t much,” Ricucci said. “A lot of people were using them and didn’t have policies on them yet.”

Finding stolen cars faster

The technology first came to the Washington region in 2004 as a pilot program. During an early test, members of the Washington Area Vehicle Enforcement Unit recovered eight cars, found 12 stolen license plates and made three arrests in a single shift. Prince George’s police bought several units to help combat the county’s crippling car theft and carjacking problem. It worked.

“We recover cars very quickly now. In previous times that was not the case,” said Prince George’s Capt. Edward Davey, who is in charge of the county’s program. “Before, they’d be dumped on the side of the road somewhere for a while.”

Now Prince George’s has 45 units and is likely to get more soon.

“The more we use them, the more we realize there’s a whole lot more on the investigative end of them,” Davey said. “We are starting to evolve. Investigators are starting to realize how to use them.”

Arlington police cars equipped with the readers regularly drive through the parking garage at the Pentagon City mall looking for stolen cars, checking hundreds of them in a matter of minutes as they cruise up and down the aisles. In Prince William County, where there are 12 mobile readers, the units have been used to locate missing people and recover stolen cars.

Unlike in the District, in most suburban jurisdictions, the units are only attached to police cars on patrol, and there aren’t enough of them to create a comprehensive net.

Virginia State Police have 42 units for the entire state, most of them focused on Northern Virginia, Richmond and the Tidewater area, and as of now have no fixed locations. There is also no central database, so each unit collects information on its own and compares it against a daily download of wanted vehicles from the FBI and the state.

But the state police are looking into fixed locations that could capture as many as 100 times more vehicles, 24 hours a day, with the potential to blanket the interstates.

“Now, we’re not getting everything — we’re fishing,” said Sgt. Robert Alessi, a 23-year veteran who runs the state police’s program. “Fixed cameras will help us use a net instead of one fishing pole with one line in the water waiting to get a nibble.”

Beyond the technology’s ability to track suspects and non-criminals alike, it has expanded beyond police work. Tax collectors in Arlington bought their own units and use the readers to help collect money owed to the county. Chesterfield County, in Virginia, uses a reader it purchased to collect millions of dollars in delinquent car taxes each year, comparing the cars on the road against the tax rolls.

Police across the region say that they are careful with the information and that they are entrusted with many pieces of sensitive information about citizens, including arrest records and Social Security numbers.

“If you’re not doing anything wrong, you’re not driving a stolen car, you’re not committing a crime,” Alessi said, “then you don’t have anything to worry about.”


Graphic: Who has LPR cameras and how long do police hold on to information?


Even as Pr. George’s workers endure pay freeze, raises planned for leaders

Thieves target high-end eyewear stores

Federal agency parties take a holiday

Man injured in jump from Va. parking garage