The technology mounted on many law enforcement agencies' vehicles throughout the country is quite advanced, including here in Tennessee.
They are called License Plate Readers, or LPR, and they scan thousands of drivers' plates in a day. However, those devices are not without controversy.
With a slight beeping sound, the LPR snaps a photo of a driver's tag.
Once a picture appears on the screen, it immediately enables law enforcement to check for suspended licenses, stolen vehicles or worse, cars tied to wanted criminals on the loose or connected to Amber Alerts.
The photos are checked against lists from more than 12 databases from both the Feds and within local departments, which are downloaded daily.
"I've never went a full day and not got a hit," said Tennessee Highway Patrol Trooper Dwayne Stanford.
The system is efficient.
"A trooper can read 100 to 150 license plates per shift and check them out through his computer and LPR can run 5,000 tags through an LPR per shift," explained Tennessee Highway Patrol Colonel Tracy Trott.
Since implementing LPRs back in 2010, the information that is collected has enabled the Tennessee Highway Patrol to stop multiple terrorists on the FBI watch list, arrest several sex offenders in violation of the sex offender registry, arrest more than 30 wanted individuals, locate numerous missing persons, recover 40 stolen vehicles and license plates, and arrest and cite almost 200 people for driving on a suspended or revoked license.
Despite all the success, there are still concerns about how it is used.
"With these new innovations come civil liberties concerns. In this instance, privacy concerns," said Hedy Weinberg Executive Director, American Civil Liberties Union of Tennessee.
The primary concern is how long the location and movements of people are kept on databases after LPR cameras capture them.
Information on just about anyone can be kept up to a year. So if your tag was run, that means your information can be kept for a year even if you don't do anything wrong.
Privacy advocates feel the data should be destroyed after 24 or even 48 hours if no "hit" has been made for innocent drivers.
"Scanners play a very important role in law enforcement at the same time we need to recognize that there needs to be retention policies in place to ensure the privacy rights of all Americans," said Weinberg.
"We may adjust that down at some point and time, but we're not using it to track any body's movements we just keep the data in case something comes up in an investigation," said Colonel Trott.
LPR technology has held up in court. The U.S. District Court ruled no violation of the forth amendment, which protects U.S. citizens against unreasonable search and seizure.
One of these units costs $20,000.
THP usually purchases them with grant money.
The department started off with eight LPRs back in 2010. Currently 48 trooper vehicles throughout the state are equipped with the technology.