Chris Monroe/CNET

In May, police in Hammond, Indiana, got a suspicious-person alert from a concerned resident. She could see a man, she told officers, through her Ring smart doorbell.

The resident had already sent police another message, along with footage from her internet-connected video doorbell, about an earlier incident. Now the resident was even more frightened, having watched a new incident unfold on her phone through a live feed from her Ring app.

She sent police the video recorded from the doorbell. Police immediately knew the man wasn't a criminal.

"It was one of our detectives. He was going there to interview the person for whatever the situation was," said Steve Kellogg, a public information officer for Hammond Police, adding that the cop was wearing plain clothes but had a badge around his neck. The badge was out of the Ring camera's line of sight, but the resident would have spotted it immediately had she gone to the door, the officer added.

"He's clearly on the camera saying he's with the police department," Kellogg said.

Now playing: Watch this: Ring's partnership with police means more false alarms

The incident is among the growing number of false alarms involving Ring cameras, which have spread around the country as police departments partner with Amazon's smart doorbell company. False alarm calls are nothing new, but police say the Ring doorbells make it easier for citizens to report anything they find suspicious and send video for law enforcement to review.

Ring and police have promoted these partnerships on social media, often demonstrating their value by highlighting incidents in which Ring has stopped package thefts.

"The more people involved in your neighborhood watch, the safer our neighborhoods become," Ring says on its website. "Ring connects citizens with each other and local law enforcement to make a true impact on your community."

Ring's limitations, however, aren't prominently featured.

Once you start having all of these cameras and start linking them to automatic notifications, the public may get the sense that crime is on the rise when it actually isn't. Dave Maass, senior investigative researcher at the Electronic Frontier Foundation

In towns where police have signed up for Ring, officers told CNET that having the extra sets of eyes in neighborhoods doesn't mean the police are solving more crimes. In some cases, it simply means there's more worry among residents.

At the International Association of Chiefs of Police conference in May, police from Chandler, Arizona, said apps like Ring's Neighbors have prompted residents to believe crime is prevalent even though violent crime is at historic lows in the city, according to notes provided by Dave Maass, a senior investigative researcher at the Electronic Frontier Foundation, who attended the conference.

"Once you start having all of these cameras and start linking them to automatic notifications, the public may get the sense that crime is on the rise when it actually isn't," Maass said.

Detective Seth Tyler, a Chandler police public information officer, told CNET that the department has received an average of two alerts a day from residents through the Neighbors app since the department partnered with Ring in April. Typically, the footage is of cars driving in neighborhoods, people walking or strangers at doorsteps, Tyler said. These aren't crimes, but Chandler police will still investigate those leads, the officer said.

"Some people are better than others at determining crimes," Tyler said. "But from our perspective, I can tell you that we would be more than happy to investigate all of those."

The department's crime prevention unit has three officers responsible for watching footage from Ring's app and investigating leads. Last December, Ring CEO Jamie Siminoff and Neighbors general manager Eric Kuhn told CNET that roughly one in three posts shows crimes or public safety issues. About 65 percent of posts on Neighbors are "suspicious behavior" or solicitors and strangers on people's property.

"Ring is proud of how engaged our users are within their communities, which includes alerting local law enforcement if something seems out of the ordinary," a Ring spokesperson said in a statement. "Reaching out to local law enforcement for help is exactly what the public has been taught to do and gives local law enforcement the chance to decide if further action is needed. This is a key part of the community's relationship with law enforcement, and that is not exclusive to owning a Ring device or engaging on the Neighbors app."

Amazon doesn't disclose how many police departments it works with, but a CNET investigation found more than 50 law enforcement agencies had developed relationships with the Ring business over the last two years. Fight for the Future, a tech-focused nonprofit, has created an interactive map to identify where police have partnered with Ring. Motherboard reported that Ring told police it's partnered with 200 law enforcement agencies in the US.

Amazon purchased Ring in 2018 for $839 million, according to SEC filings. At the time, analysts forecast that more than 3.4 million video doorbells would be sold that year.

Some Ring true

Not all calls to Ring are false alarms.

The cameras have helped solve plenty of crimes, including a double homicide in Gary, Indiana. Prosecutors in a murder case in Texas used Ring footage to show an alleged killer entering a home. In Bloomfield, New Jersey, an entire town covered in Ring cameras, the system has helped solve an armed robbery as well as car thefts, according to Capt. Vince Kerney, Bloomfield's detective bureau commander.

Still, there's often more footage of innocent behavior than there is of actual crime, police say.

Kerney recalls an incident in which his department received footage from four homes about a truck suspected of following a child around. They were able to identify the truck based on the video provided. After investigation, it turned out to be a false alarm.

"There was no crime that was being committed. It was just a coincidence that this person pulled over in front of a kid, and he got scared and ran away," Kerney said.

It's unclear how many false alarms have been sent to police. Amazon doesn't provide overall statistics on usage of the device.

In February, The Outline detailed an incident in which a resident called police after seeing footage of someone walking through her front door in California. The dispatcher helped the caller realize she was watching footage of herself entering her home.

Though Ring has helped police solve some crimes, it's unclear if the technology has any significant effect on crime rates. Amazon says it does, citing a 2015 pilot program in Los Angeles that found Ring doorbells helped to more than halve burglaries. Last October, MIT Technology Review looked at crime data and found the study wasn't as accurate as its authors claimed.

In some cases, police don't get information from Ring or Neighbors quickly enough to be useful. In Hampton, Virginia, police put out an alert for a missing person on Neighbors, asking residents to send any footage they could. The missing person was found before any footage was received, police said.

More footage, more problems

In March, Eric Piza, an associate professor at the John Jay College of Criminal Justice, released a study that found surveillance cameras were mostly effective when they were being actively monitored. They did little to reduce crime rates if police were receiving footage after an incident.

With Ring, police are receiving even more footage, and Piza found that officers often don't have resources dedicated to watching it all.

"What my research has found is that police can have too many videos to actively monitor," he said. "If police plan on integrating Ring footage into their operation, technology requires manpower to be effectively used."

Because Ring partnerships give citizens a direct line to police through the Neighbors app, Piza is concerned about overreporting of innocuous activities. In February, Motherboard reviewed more than 100 Neighbors posts, the majority of which were reports of people of color going about daily life.

We've seen from research that people are not the best judges of criminal behavior. Eric Piza, associate professor at the John Jay College of Criminal Justice

Often, the footage simply captures people walking through a neighborhood. They aren't engaged in any activity that could be considered suspicious, Piza said.

Ring's relationship with police has created more cameras in residential neighborhoods and more opportunities to find footage to solve crimes, but it's also opened up the pipeline for unfounded concerns.

"We've seen from research that people are not the best judges of criminal behavior," Piza said. "Especially recently, with white citizens reporting black citizens for innocent and innocuous behavior."