Three license plate readers that Menlo Park police began using this summer captured images of more than 250,000 plates between July 1 and Oct. 1, according to a police staff report.

Out of all those images, however, only one could be tracked to a crime. Police recovered a stolen car and arrested the thief.

The readers, which cost a total of $57,914, are mounted on the roofs of two marked patrol cars and one unmarked vehicle used by detectives. Each has four high-speed cameras that take pictures of license plates in front of, behind and alongside police cars. The collected data is then uploaded to a server managed by the Northern California Regional Intelligence Center, part of the Department of Homeland Security.

According to the staff report, 263,430 license plates were photographed in the first three months that the readers were used. Of those, 141 plate numbers registered as a “hit,” matching those of vehicles on an active wanted list that were stolen or associated with missing people.

“The vast majority of the hits were subsequently deemed to be a ‘false read’ after further review by the [Automated License Plate Reader] operator,” the report states.

Police spokeswoman Nicole Acker said a “false read” occurs when the photo of a license plate differs from the computer-generated image of the plate.

“A simplified example of a type of false read would be when an 8 is read as a B and vice versa,” she wrote in an email.

The Menlo Park City Council in September 2013 approved the license plate readers’ purchase and several months later adopted a privacy ordinance that requires data to be deleted six months after being obtained unless it is part of an ongoing investigation. The police department is supposed to produce quarterly reports detailing the number of plates captured citywide, how many were on the wanted list, and the number of police inquiries they generated.

The report, listed as an informational item on the council’s Nov. 18 meeting agenda, is the first one produced since the readers were obtained.

Police Commander David Bertini said concerned Menlo Park residents came up with the idea of investing in license plate readers.

“Citizens of the Belle Haven came to us during neighborhood meetings and wanted to know what could be done to reduce the crime in that specific neighborhood,” he said. “And it was the residents who said, ‘Hey, why don’t you put [surveillance] cameras up there? Why don’t you put license plate readers out there?’ …

“I don’t want to jinx this, but I have to tell you, since January 1, we have not had one shooting in the Belle Haven, which is unheard of in that neighborhood.”

Bertini said the license plate readers’ role in locating stolen vehicles is “almost secondary” to its value as a “deterrent to bad guys” and an investigative tool for solving crimes. It would be premature to judge the technology’s effectiveness after only three months, he added.

“Why don’t you ask me in two or three years and I can probably give you a better idea,” Bertini said.

Mayor Ray Mueller said Friday that although license plate readers are “another tool in the arsenal of our police department,” their use was hotly debated by council members.

“To my knowledge, we are the first city to actually enact an ordinance to regulate how long the city can keep drivers’ data,” he said. “Not only can the information only be kept for six months, but it is an ordinance, which means that if anyone, including a police officer or government official, misuses that information, they have committed a crime.”

Mueller also noted that such technology requires a continuing assessment of public safety concerns versus the community’s right to privacy.

“Technology is improving,” he said. “Technology such as this one, while it may be OK with safeguards today, in the future, it may not be. As the government’s ability to aggregate information and apply complex algorithms and artificial intelligence to track people’s lives increases, the balancing test of whether or not that technology is infringing upon the public’s right to privacy will change. It’s something that public servants need to continually monitor and appraise.”

Email Rhea Mahbubani at rmahbubani @dailynewsgroup.com or follow her at twitter.com/RMahbubani.