An Amazon-owned home security company has netted hundreds of police contracts — including nearly a dozen in the Bay Area — that could help solve neighborhood crime. But critics say the quick spread of such partnerships has skirted public oversight, turned police departments into corporate marketing machines and threatened the privacy of innocent people.

Ring, well known for its popular “video doorbells,” has capitalized on a rise in package thefts and law enforcement’s growing interest in private surveillance by teaming up with police departments in San Jose, South San Francisco, Milpitas, Union City, Walnut Creek, Novato, Foster City and Hercules, as well as the Marin County Sheriff’s Office. All but two of these agencies signed agreements in the past three months.

Their officers have the use of a law enforcement portal on Ring’s Neighbors app to request and obtain videos within a specific time frame and area from users who grant permission. Residents’ location and identity remain anonymous. More than 900 agencies in the country had contracts with Ring as of Feb. 6, when the company last updated its information.

Bay Area agencies laud the agreements, which come at no cost. The technology helped solve two package thefts in Milpitas during the holidays, police Capt. Raj Maharaj said. Five other departments said they had no examples of crimes solved yet, pointing instead to the potential benefits of their Ring partnerships.

“If a crime does occur, it just gets the info to those that are entrusted to help solve the crime quicker. That’s a point you can’t argue,” San Jose Police Chief Eddie Garcia said.

But some cities have raised privacy concerns about Ring’s services, prompting a congressional investigation last year and alarming watchdogs.

The cameras, they say, intrude on other people’s privacy by recording motion detected up to 30 feet away. The rights of passersby such as dog walkers, mail carriers, and children playing across the street are being violated without their consent, said Mike Katz-Lacabe, a member of Oakland Privacy, a coalition of people who are concerned about privacy and surveillance.

“Personally, I don’t want to live in a surveillance dystopia where my neighbors are essentially spying on me on behalf of my local law enforcement,” he said.

The Neighbors app, Katz-Lacabe said, can also tie up police resources when they’re not needed, stoke fear and spark discrimination.

“I think it tends to lead to a perception that crime is greater than it is, even though it’s at historic lows,” Katz-Lacabe said. “It tends to focus on black and brown people, because the people who are buying Ring cameras oftentimes are in wealthier neighborhoods with less minorities, and in that case, anybody who doesn’t look like the people who live in that neighborhood are going to be found suspicious.”

Though violent crime rates have fallen in recent years, property crimes increased in Santa Clara, Alameda, Contra Costa and San Francisco counties in 2017, according to the Public Policy Institute of California. San Francisco had the highest per-capita rate of property crime of any major U.S. city that year, with 6,168 crimes per 100,000 people — largely because of the rise in auto break-ins.

Foster City police signed an agreement with Ring in May, and have sent out just one request for footage from residents, said Lt. William Sandri, a department spokesman. The residents did not reply.

Still, Sandri said, the technology could help link a suspect to several crimes. “It’s not going to solve every crime, but it just provides us with another lead or another angle to work,” he said.

In late January, Oakland police sought help from the public by posting photos and video captured by a Ring doorbell camera on social media. The images showed two people violently robbing a woman on her doorstep. Although the crime remains unsolved, department spokeswoman Officer Johnna Watson said that security videos are “always helpful” because they can help identify a weapon and provide a suspect description.

Oakland police are in the early stages of conversations with Ring about becoming a partner.

San Francisco police have not signed a contract with Ring, but officers use home security footage provided by residents for investigations. Last year, Cole Valley resident Deanna Hodgin said, she was getting ready for church when her husband called from London. Ring had notified him of an intruder fiddling with the lock on their front door. Her husband shouted at the man until he left and sent the video to police, but Hodgin was too scared to go to church.

The 58-year-old resident said her family purchased the device — and plan to get more — after their home and car were broken into several times. She understands privacy concerns but says she has to protect herself.

“After you realize that you’re ... the prey,” she said. “You sort of lose the concern for the rights of people who have no concern for your rights.”

Ring said its mission is to make neighborhoods safer and that it upholds user privacy standards. No one can view video recordings without the resident’s permission, for example, and Ring encrypts communication between devices and the Amazon server that stores the videos, according to the company, and it does not knowingly collect information about children younger than 13.

“We’ve seen many positive examples of residents and local police engaging on the Neighbors app and believe open communication is an important step in building safer, stronger communities,” Ring officials said.

Video doorbells send a notification to camera owners, who can tap in to the live stream and initiate two-way audio. The cameras capture clear footage at night, too, according to the company. Ring then stores the video on a cloud server reserved for users who pay for a separate plan.

Law enforcement officers must cite a specific active investigation and can request footage only within a limited time and from a distinct area related to that case. Customers can decide whether to share all relevant footage, choose certain videos to share, decline to provide any of the doorbell recordings, or opt out of all future requests.

Critics, including at least one senator, argue that there is no evidence that Ring cameras make communities safer, and they point to a string of high-profile hacking incidents as proof of the contrary.

Sen. Ed Markey, D-Mass., led a months-long investigation into Ring by the Commerce, Science and Transportation Committee that found “an alarming disregard for basic privacy protections for consumers.”

Fight for the Future, a nonprofit digital rights advocacy group, blasted Ring in an open letter in October signed by more than 30 civil rights groups. The letter followed a Washington Post report that 400 police agencies had entered into agreements with the company as of August.

Evan Greer, director of Fight for the Future, said the lack of public oversight and accountability of these partnerships is a fundamental problem.

“If the cops in your neighborhood wanted to put a surveillance camera on everyone’s front door, they would clearly have to go seek approval from a city council or a mayor or some elected officials,” Greer said. “In this case, Amazon is ... providing a seamless process by which police can vacuum up that footage, store it indefinitely and use it for all sorts of abusive purposes without any meaningful oversight or accountability.”

Ring said it is careful with customer data. “We maintain administrative, technical and physical safeguards designed to protect personal information against accidental, unlawful or unauthorized destruction, loss, alteration, access, disclosure or use,” its privacy notice says.

The company collects users’ online browsing activity, the notice says. It relies on residents to follow privacy and video surveillance laws, which vary by jurisdiction, such as posting a notice that they are recording.

Another worry of critics is Ring’s oversight of police departments’ public communications, which they say relinquishes control of government employee resources. Departments must seek written approval from the company for news releases that mention Ring or include the company’s logo, according to contracts obtained by The Chronicle.

Officer Mike Howard, a spokesman for Novato police, said his department allowed Ring to review its first news release to make sure it was factually correct. But the department has since avoided using Ring’s name to maintain control of its communications.

“Quite honestly, it’s because we don’t want the appearance that Ring writes our press releases, because they don’t,” Howard said.

Chief Garcia said he also signed a contract allowing Ring to review the San Jose Police Department’s news releases, but said he would sever the contract if Ring were to request substantial changes.

“Although it’s in the contract, no one controls the message of this Police Department other than me,” Garcia said.

Not every local agency maintains the same level of independence. Sgt. Brent Schneider, a spokesman for the Marin County Sheriff’s Office, said he planned to tell a Ring representative that he had spoken with The Chronicle about Ring, as the company requested.

Greer said these partnerships require the oversight of elected officials to ensure they are not being abused.

“I think it’s very Silicon Valley to assume we can either have a world with package theft, or we can live in a totalitarian surveillance state — but you can’t do both,” she said. “Given the choice, I’d rather live in a world with a little bit of package theft and a little less fascism.”

Anna Bauman is a San Francisco Chronicle staff writer. Email: anna.bauman@sfchronicle.com Twitter: @abauman2