Karen Thornburg called St. Paul police time and again — after the house next door was torched, when her children were getting harassed, after a neighbor kid drop-kicked a cat. Each time, police told her they needed proof to make an arrest.

So she installed video cameras at her home, in her yard, her garage and at the homes of a half dozen Dayton's Bluff neighbors. Now, Thornburg said, her area is so blanketed with security cameras that criminals dare not hit her block. And when they do, such as during a September shootout between two cars that sent a bullet into a neighboring house, police used her video to identify suspects.

"It's a good deterrent," she said of the dozens of cameras installed by her electrician husband. "Everybody is leaving my neighborhood alone."

A vast network of smart home surveillance systems like Ring and Nest is at the heart of a new kind of neighborhood watch in the Twin Cities and beyond. Whether posting video to social media of porch pirates stealing packages or capturing footage of drive-by shootings, law enforcement officials say an increasing number of residents are sharing more digital evidence than ever before.

So much so that a growing number of police departments are enlisting homeowners and their equipment to better track and attack crime. In the meantime, organizations like the American Civil Liberties Union urge caution when using such devices and sharing the data they gather.

Ring, owned by Amazon, has partnered with more than 400 agencies nationwide — including at least 15 in Minnesota — to identify relevant video footage recorded in their area. When a crime occurs in one of their partners' jurisdictions, Ring contacts nearby customers to ask permission to share their video with authorities. Participation is voluntary and users can opt out at any time. The partnership also allows police to join Ring's Neighbors app, which encourages residents to post footage of suspicious activity.

After the program launched in 2018, the tech company pitched it to law enforcement as an investigative tool that would bolster community engagement and make neighborhoods safer. Agencies were offered access to the system at no cost, according to a copy of the basic contract obtained by the Star Tribune.

Police and county sheriff's departments from Brainerd to Rochester jumped at the opportunity.

In Shakopee, where streets are peppered with cameras, officials saw a chance to leverage the existing Ring network to complement on-the-ground police work. Since partnering with Ring last August, Chief Jeff Tate has made a handful of video requests to help catch home intruders and serial burglars. For decades, officers have urged gas stations and area businesses to share security footage that might aid their investigations. Tate said those often grainy videos pale in comparison with modern-day Ring cameras, which capture sharp, wide-angle images — even in the dark.

"The quality speaks for itself," said Tate, who recently bought a camera of his own. "We'd be silly not to use that as a tool to solve cases."

Minneapolis and St. Paul, the two largest police departments in the state, chose not to partner with a specific company because residents willingly hand over so much material already. Asking homeowners whether they keep surveillance footage on their property has become a standard question for Minneapolis police officers canvassing neighborhoods over the last 18 months.

"People have been so gracious about sharing their video with us that we haven't needed to forge a relationship with corporate entities," said police spokesman John Elder. In the city's latest high-profiling killing, a security camera positioned at a home in Maple Grove helped investigators piece together the kidnapping of Monique Baugh.

Video caught Baugh, a 28-year-old real estate agent, pulling up to the house and a U-Haul repositioning to back up against the garage doors, according to a search warrant affidavit. That same vehicle was spotted in the north Minneapolis alley where her body was later dumped.

Four have since been charged in connection with her murder, including two men indicted Friday.

However, privacy advocates say there may be unintended consequences to recording and sharing all that video.

University of Minnesota Law School Prof. JaneAnne Murray says a network of cameras could also be recording the everyday movements and activities of scores of people. Such aggregate data could be paired with facial recognition software by police, corporations or political campaigns to study and follow the movements of anyone within range of the cameras. Upload all of that to the cloud, Murray said, and a range of privacy issues arise.

"This is a powerful tool, and before we embrace it, we need to think of all the ramifications, and set limits on its usage," she said. "Our founders, who enshrined the right to be free from unreasonable searches and seizures in our Constitution, would be turning in their graves at the power of modern technology to track and store our movements in perpetuity."

Law enforcement downplays those concerns, maintaining that it's not a spy tool. Investigators cannot tap into a homeowner's camera and they don't have access to a map identifying where devices are located in their communities. And users can remain anonymous, unless they specifically agree to share their personal information with police.

Fears about a potential surveillance society don't scare Jeff Magee, a retired St. Paul field agent with the Bureau of Alcohol, Tobacco and Firearms and Explosives (ATF). Intelligent cameras are the natural progression of technology, he said, following the use of license-plate readers and facial recognition.

"Society has changed. The old way of policing is gone," Magee said from a St. Paul coffee shop, noting that he's under constant surveillance when he steps outside his home. "There is no real privacy."

In recent years, Ring found success marketing its motion-activated doorbell cameras as an affordable alternative to monthly fee-based security systems like ADT. Standard Ring doorbell cameras run $99, with a recurring $3 monthly fee for users who want the footage stored. The company retains those recordings for up to two months.

Nancy Hochschild of St. Paul was among the first on her North End block to get a doorbell camera in 2017, after thieves pilfered packages from her front porch. It didn't take long for her to realize their value. The cameras have captured multiple gunshots in the area — video she has turned over to St. Paul police four times.

"Now I need [cameras] in the back, because they broke into our garage," she said. "And they stole my son's scooter from our van."

To Hochschild, the technology offered a complement to traditional neighborhood crime watches, which are becoming increasingly digital. She started a Facebook page devoted to calls heard over the city's police and fire scanners. Unlike many of her neighbors, however, she doesn't want to post videos on social media due to public safety concerns. She said she shares what her camera captures only with police.

Longtime St. Paul resident Dick Kelly mounted video cameras both inside and outside his home for the peace of mind. Last year, the cameras caught an unknown man with a dog attempting to open Kelly's back door. He later posted the video as a "be on the lookout" warning to neighbors.

Miranda Meyer of St. Paul has strategically placed "more than four" cameras around her property.

"I definitely think that it's making troublemakers think twice, knowing that they could potentially be caught red-handed," she said.

The Associated Press contributed to this report.