License reader lawsuit can be heard, appeals court rules

SFPD sued by woman pulled over in high-risk stop after vehicle mistakenly identified as stolen

A federal appeals court this week ruled that a woman's Fourth Amendment rights may have been violated when San Francisco police arrested her after an automated license plate reader mistakenly identified her car as stolen. The decision provides fodder to privacy advocates calling for restrictions on the use of the technology.

The U.S. Court of Appeals for the Ninth District Tuesday reversed a district court ruling saying the police made the arrest in good faith. A three-judge panel at the appellate court held that a reasonable jury could indeed find that the woman's Fourth Amendment rights against unreasonable search and seizure had been violated. The case was remanded back to the district court.

The case involves Denise Green, 47, who was stopped, handcuffed and detained briefly by multiple police officers with drawn guns, on a March night in 2009.

The incident was triggered when Green's car passed a police cruiser whose ALPR mistakenly determined that the vehicle was stolen. According to the appellate court's description of the incident, the photograph taken by the ALPR was blurry and illegible because of darkness.

The police officer operating the license plate reader radioed in a description of Green's vehicle and provided the incorrect license plate number from the ALPR read to dispatch. He did not confirm the tag number visually.

Dispatch quickly identified the plate as belonging to a stolen vehicle prompting a sequence of events that ended with Green being stopped by multiple police cars, handcuffed at gunpoint and detained while officers searched her car and person before letting her go.

Green filed a lawsuit against San Francisco Police Department, the city, county and the police officer in charge of the incident contending Fourth Amendment violations as well as unreasonable use of force and other charges. She asked the court for a summary judgment on her claims.

The U.S. District Court for the Northern District of California rejected Green's motion and agreed with the SFPD's assertion that they had acted under reasonable suspicion.

The judges at the appellate court rejected that argument. In an 18-page opinion, the judges noted that ALPRs have been known to make mistakes and that police should know not to make traffic stops based on an ALPR read alone.

"It is undisputed that the ALPR occasionally makes false 'hits' by misreading license plate numbers and mismatching passing license plate numbers with those listed as wanted in the database [of wanted numbers]," the appeals court said in its ruling.

Because of the known flaws in the system, police officers are required to visually confirm the validity of a "hit" before initiating a high-risk felony stop.

In Green's case, the police officer in charge of the stop had plenty of opportunity to visually verify the plate number as well as the make and model of her vehicle, which were different than the stolen vehicle, the appeals court judges said.

At the time of the incident, SFPD had no rules stating who was responsible for verifying the physical license numbers in ALPR hits, not "the camera car operator or with the officer conducting the subsequent stop," the opinion read.

Police departments across the country are now using automated license plate readers in increasing numbers to track stolen vehicles and those associated with active investigations. In many cases there are few, if any, policies regarding the use of LPRs and the data collected by the devices.

Privacy advocates have expressed concerns that the data collected by the devices gives police the ability to monitor an individual's movements in intrusive detail. Organizations like the Electronic Frontier Foundation have noted that many police departments already have massive databases of information gathered by ALPRs with no guidelines or transparency regarding use of the data.

"Using tools like license plate readers and pre-crime 'intelligence-led' policing algorithms, police officers are relying more and more on computers to tell them who is dangerous, who is wanted for crimes, and who is suspect," the American Civil Liberties Union" said in a blog post responding to the Ninth Circuit decision.

"While police offices can make mistakes on their own, without a helping hand from malfunctioning technological systems, the buck must stop with the officers in the flesh," the ACLU said.

Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan or subscribe to Jaikumar's RSS feed. His e-mail address is

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