A crime-fighting tool until now kept under wraps by the Hennepin County Sheriff's Office is drawing both praise as a critical asset in the hunt for bad guys, but also concern in an era of growing surveillance.

The Sheriff's Office is the only law enforcement agency in the state to offer facial recognition technology, once the domain of the military and top national intelligence investigators. The software now generates leads on drug dealers, bank robbers, burglars and other conventional criminal suspects.

Known formally as Image Identification Technology, it works by identifying thousands of points on a person's face to determine such things as the distance between the eyes or the shape of the lips. It takes about 30 minutes to find a possible match.

While the Sheriff's Office began using the software in August 2013, its use came to the forefront last week following lengthy efforts in court by Tony Webster, a self-employed software engineer who lives in Minneapolis, to compel the Sheriff's Office to release its e-mail communication about the technology. Abiding by the court order, the Sheriff's Office provided Webster access to the e-mails.

"I was surprised to learn they had been using the technology for three years and there was no public disclosure about it," Webster said. "I don't think Minnesotans would be against the technology, but it's going to be a big issue to watch."

On the day Webster published a blog post detailing what he discovered, the Sheriff's Office posted a Facebook statement defending facial recognition technology and "dispelling myths," Hennepin County Sheriff Rich Stanek said. The post explained how the software was used to identify Anthony M. Rechichi, who is a suspect in the May 20 robbery of Hiway Credit Union in Minneapolis and a person of interest in another bank robbery. Rechichi turned himself in last week and was charged with aggravated robbery. The Sheriff's Office kept word of the software quiet to stay a step ahead of criminals, Stanek said.

"Ours is a law enforcement agency; we make no apology for our mission to solve crime, or to prioritize violent crime," the Sheriff's Office post read. "And as we conduct our mandated responsibilities, we respect our laws, including data practice laws, and we respect and protect the privacy rights of all residents."

With any new surveillance advancements, critics are quick to point out the potential for abuse. Stanek said his office developed a policy and training program to guarantee the software's public safety goal isn't at the expense of civil liberties, he said.

"We attempt to match unknown criminal suspects to a database of public Hennepin County booking photos, which are public information," he said. "In the Sheriff's Office, we do not gather or retain photos real-time from cameras in the community."

The Sheriff's Office received more than 80 requests for assistance with facial recognition from other law enforcement agencies this year. Nearly half resulted in an identification, arrest or conviction, Stanek said.

Despite recognition rates of 99.7 percent for well-lit, frontal photos, security cameras often don't produce quality images, requiring extra legwork.

"The software is a cool thing, but it's not like you see on TV," he said. "It doesn't take away the human factor in solving crimes."

The next privacy debate

Facial recognition technology was first developed in the 1960s, but only recently became accurate enough for widespread use — and it has created business in Minnesota. In 2010, Maplewood-based 3M Co. paid nearly $1 billion for the California company Cogent, which develops a variety of identification systems, including iris and facial recognition technology. Another company, MorphoTrust USA, has a biometric facility in Bloomington.

The Sheriff's Office paid nearly $140,000 for its software, which was paid for by a federal grant for biometrics approved by the County Board. The office must file a quarterly report on its use, Stanek said.

The Minneapolis and St. Paul police departments and the state's Bureau of Criminal Apprehension don't use the software. The FBI declined to comment.

Spokesmen for the Hennepin and Ramsey County attorney's offices said they couldn't recall if they received cases that included facial recognition evidence. The U.S. attorney's office for the District of Minnesota said it wasn't aware of any time the technology was used as trial evidence.

Rechichi's case appears to be one of the few involving facial recognition that has been presented to the Hennepin County attorney's office for prosecution. Because it's a relatively new tool, County Attorney Mike Freeman said there could be legal challenges of its use in trial.

"Defense attorneys tried to discredit the use of DNA evidence for years, but science validated it," Freeman said. "Attorneys may fight how the facial image was obtained for recognition, but we have no problem putting that through the paces."

According to the Sheriff's Office policy on the use of facial recognition software, it will be used only to provide leads on a person believed to be involved in criminal activity and not as a substitute for positive identification. Stanek said his office has no intention to use "real-time automatic facial recognition to create a database of everywhere you go."

The executive directors from the state's County Attorney and Chiefs of Police associations haven't had discussions about facial recognition technology, but plan to address the issues in the future. It's the latest crime-fighting technology to stir debate at the Capitol over privacy concerns — following automatic license plate readers, cellphone tracking devices and body cameras — but such technology has been on the national radar for several years. In July 2012, a hearing was held by a U.S. Senate committee to address issues surrounding what facial recognition technology means for privacy and civil liberties.

Chuck Samuelson, executive director of the ACLU of Minnesota, said facial recognition software is another example of an "over-surveilled" culture.

"We have the right to be left alone in society," he said. "If the only thing they have to compare images to was mug shots, my argument would be weak. There's driver's license photos and images on Facebook."

Brooklyn Center police detective Terry Olson understands why people might raise red flags regarding privacy or civil liberty issues, but he doesn't expect any widespread abuse of the technology. His department used it to catch a man who stole several security cameras and was wanted for a string of auto thefts in Hennepin County.

"The mug shots that are used to compare images are public. And people can't expect a right of privacy if they are videotaped by a camera in a public space," he said. "The technology is no magic bullet for identification, but it can certainly point you in the right direction."

David Chanen • 612-673-4465