The Fairfax County Chief of Police is fighting a judge's ruling that would forbid the department from storing data from license-plate readers - a decision the chief says would harm the department's ability to investigate a variety of incidents and crimes.

Police point to a March 2015 investigation as proof that the license-plate readers can be instrumental.

A man under guard inside Inova Fairfax Hospital overpowered a security guard, stole her weapon, and escaped.

He then later carjacked two vehicles before being re-captured in the District.

Police say the manhunt was assisted by license-plate readers on cruisers and fixed posts around the county.

"The license plate reader system helped us determine a finite tag number and description of the car which was then used through social media to help the community find the suspect in D.C.," Police Chief Edwin Roessler said.


The chief also notes that the data has helped police find people during Silver and Amber alerts.

He says purging the data daily will impact public safety.

"The core issue here is we do not peruse the LPR system for mere curiosity or disseminate information - it is for a law enforcement purpose," he said.

But Judge Robert Smith this week ruled that the police department's policy of storing the information for nearly a year violates Virginia's privacy law.

Privacy rights advocates are calling the ruling a victory. They say the data opens the door for possible abuse.

The license plate reader system has the ability to record exactly where and when a license plate was photographed.

Police say the readers are invaluable in finding stolen cars or wanted individuals. The system sends an officer behind the wheel an alert if the reader records a plate on the so-called "hot-list."

"What I am also fearful of in this ruling is that in car video and body worn camera footage would also be subject to the same ruling and therefor make all of these IT systems which we use for public safety to accomplish our mission or preventing and fighting crime will not be of use to us," Roessler said.

According to a judge's ruling, the department is now under orders to purge the data every day.