SAN DIEGO (TIP): Facial recognition software, which American military and intelligence agencies used for years in Iraq and Afghanistan to identify potential terrorists, is being eagerly adopted by dozens of police departments around the country to pursue drug dealers, prostitutes and other criminal suspects. But because it is being used with few guidelines, it is raising questions of privacy and concerns about potential misuse.

Law enforcement officers say the technology is much faster than fingerprinting, although it is unclear on how much it is helping the police make arrests. When Aaron Harvey was stopped by the police here in 2013, an officer not only searched his car, he said, but also took his photograph and ran it through the software to confirm whether he had a criminal record, Eric Hanson, a retired firefighter, had a similar experience too, though neither of them were arrested. “I felt like my identity was being stolen. I was treated like a criminal,” Hanson said.

Lt. Scott Wahl, a spokesman for San Diego Police Department, said the department does not require police officers to file a report when they use the technology but do not make an arrest.

County documents show that in January and February, San Diego law enforcement agencies used the software on more than 20,600 occasions — finding a match to criminal records only about 25% of the time. But people who are not criminal suspects are included in the database, and the error rate for the software is as high as 20% — meaning the authorities could misidentify millions of people.