Even if you never utter a word, technology enables police to know where you've been.

The scanners capture the license plate for any vehicle that passes within view of the scanner, regardless of whether the vehicle has committed a violation, and stores the information. A police car equipped with a scanner could capture hundreds or even thousands of license plates while stationed on a roadway.

As the City Council and Mayor mulls this issue—Councilman Tom Moore hopes to continue the discussion at a town hall meeting on March 20—Patch wants to know what you think.

At issue is how long the data collected by the city's scanners should be stored. Currently Rockville's data dumps into the county's system, where the policy is to store it forever.

Here are the two main views presented to the council and mayor on Monday:

Hamill said the plate readers help police do their jobs. For one officer, using the plate reader over the course of 27 days led to:

Then there are more serious cases, like the one involving Phillip Gilberti—who spent a day fleeing from police after he shot his soon-to-be ex-wife in his minivan and threw her out onto Connecticut Avenue in Kensington. About 12 hours later, Gilberti was found dead at a residence in Rockville with a self-inflicted gunshot wound, Patch reported.

"That's good solid policing, what we expect our officers to be out here doing," Hamill said.

Hamill said police used the license plate readers to track Gilberti's movements.

"There were a lot of people who thought they might be next," Hamill said.

He also gave a hypothetical example of a cold case in which two girls go missing and a possible suspect emerges a year-and-a-half later.

"If we dump that data after a year," Hamill said, "I'm the one sitting with the mother and father and says, 'You know, we might have been able to solve this case, but I had to dump the data. I can't help you and it's my fault. I'm sorry.'"

ACLU and Electronic Privacy Information Center: Unfettered data storage is an invasion of privacy

In 2011, Rockville's three license plate readers submitted data for 101,000 license plates, according to ACLU attorney David Rocah.

Rocah and Electronic Privacy Information Center's Open Government Director Ginger McCall said the problem isn't with police use of license plate readers but rather the privacy issues that arise from retaining and aggregating the data they collect and what happens outside the scope of immediate use.

Rocah said, as part of a broader ACLU initiative, he requested from the state of Maryland any license plate data that may have been collected on him.

"And sure enough—even though as far as I know, I'm not suspected of any wrong-doing, my license has never been suspended, I believe I've never so much as gotten a speeding ticket—the state of Maryland has [automatic license plate reader] data on me," Rocah told the mayor and council Monday. "In fact, in some ways knows more about me and my movements than I do."

When addressing the mayor and council, McCall cited U.S. Supreme Court Justice Sonya Sotomayor's concurring opinion in United States v. Jones. In the case, law enforcement placed a hidden GPS device on a suspect's vehicle in order to track his movements, which the Supreme Court determined violated the Fourth Amendment.

"GPS monitoring generates a precise, comprehensive record of a person's public movements that reflects a wealth of detail about her familial, political, professional, religious, and sexual associations. … Disclosed in [GPS] data . . . will be trips the indisputably private nature of which takes little imagination to conjure: trips to the psychiatrist, the plastic surgeon, the abortion clinic, the AIDS treatment center, the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar and on and on. … The Government can store such records and efficiently mine them for information years into the future."

More recently in Virginia, Attorney General Ken Cuccinelli issued an opinion limiting the use of police license-late cameras, The Washington Post reports, which is likely to restrict how police track cars.

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Speak out: What do you think? How long should Rockville City Police hold onto data from license plate readers? Should police have indefinite access? Is a year reasonable? Is one year too long? Should public policy do more to set limits on how such data is handled? Post your comments below.

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Editor's note: This article has been updated since it was originally published. Ginger McCall is the Open Government Director for the Electronic Privacy Information Center.