For months, the Washington County Sheriff's Office has been using facial recognition software developed by Amazon to identify suspects in criminal cases as many as 20 times a day, according to emails obtained by the American Civil Liberties Union.

The software, called Rekognition, can identify faces in a crowd and match images to help law enforcement officers identify people in videos or photographs.

Gresham police purchased similar technology in April, but not from Amazon.

The new tech has critics raising concerns about mass surveillance and spying.

"The technology has supercharged surveillance capacity," says ACLU of Oregon director David Rogers, "and it's primed for authoritarian government abuse."

The ACLU joined several other civil rights organizations in writing a letter to Jeff Bezos, CEO of Amazon, asking him to stop advertising and selling the Rekognition software to law enforcement agencies because the risk for abuse is too high.

"Amazon's own marketing materials read like an instruction manual for an authoritative government control," Rogers says.

WCSO spokesman Deputy Jeff Talbot says the agency only uses mugshots it already possesses to identify suspects in video or photos using Amazon's Rekognition technology.

He also says the agency has made an effort to inform the public that it is using the facial recognition software, pointing to a handful of recent, local TV news stories that discussed cases solved using Rekognition.

In late April, more than a year after WCSO started using Rekognition, the agency adopted a policy that acknowledges some of the concerns raised by advocates.

"The Sheriff's Office recognizes that facial recognition technology is a powerful tool to identify people and enhance public safety, but that it also has significant potential privacy implications if not used appropriately," the policy says.

Correction: This story originally said that Gresham Police bought facial recognition software from Amazon. In fact, they purchased the software from another company called Vigilant Solutions. WW regrets the error.