When detectives in a Phoenix suburb arrested a warehouse worker in a murder investigation last December, they credited a new technique with breaking open the case after other leads went cold.
The police told the suspect, Jorge Molina, they had data tracking his phone to the site where a man was shot nine months earlier. They had made the discovery after obtaining a search warrant that required Google to provide information on all devices it recorded near the killing, potentially capturing the whereabouts of anyone in the area.
Investigators also had other circumstantial evidence, including security video of someone firing a gun from a white Honda Civic, the same model that Mr. Molina owned, though they could not see the license plate or attacker.
But after he spent nearly a week in jail, the case against Mr. Molina fell apart as investigators learned new information and released him. Last month, the police arrested another man: his mother’s ex-boyfriend, who had sometimes used Mr. Molina’s car.
Jorge Molina in Goodyear, Ariz. Detectives arrested him last year in a murder investigation after requesting Google location data. When new information emerged, they released him and did not pursue charges. Alex Welsh for The New York Times
The warrants, which draw on an enormous Google database employees call Sensorvault, turn the business of tracking cellphone users’ locations into a digital dragnet for law enforcement. In an era of ubiquitous data gathering by tech companies, it is just the latest example of how personal information — where you go, who your friends are, what you read, eat and watch, and when you do it — is being used for purposes many people never expected. As privacy concerns have mounted among consumers, policymakers and regulators, tech companies have come under intensifying scrutiny over their data collection practices.
The Arizona case demonstrates the promise and perils of the new investigative technique, whose use has risen sharply in the past six months, according to Google employees familiar with the requests. It can help solve crimes. But it can also snare innocent people.
Technology companies have for years responded to court orders for specific users’ information. The new warrants go further, suggesting possible suspects and witnesses in the absence of other clues. Often, Google employees said, the company responds to a single warrant with location information on dozens or hundreds of devices.
Law enforcement officials described the method as exciting, but cautioned that it was just one tool.
“It doesn’t pop out the answer like a ticker tape, saying this guy’s guilty,” said Gary Ernsdorff, a senior prosecutor in Washington State who has worked on several cases involving these warrants. Potential suspects must still be fully investigated, he added. “We’re not going to charge anybody just because Google said they were there.”
It is unclear how often these search requests have led to arrests or convictions, because many of the investigations are still open and judges frequently seal the warrants. The practice was first used by federal agents in 2016, according to Google employees, and first publicly reported last year in North Carolina. It has since spread to local departments across the country, including in California, Florida, Minnesota and Washington. This year, one Google employee said, the company received as many as 180 requests in one week. Google declined to confirm precise numbers.
The technique illustrates a phenomenon privacy advocates have long referred to as the “if you build it, they will come” principle — anytime a technology company creates a system that could be used in surveillance, law enforcement inevitably comes knocking. Sensorvault, according to Google employees, includes detailed location records involving at least hundreds of millions of devices worldwide and dating back nearly a decade.
The new orders, sometimes called “geofence” warrants, specify an area and a time period, and Google gathers information from Sensorvault about the devices that were there. It labels them with anonymous ID numbers, and detectives look at locations and movement patterns to see if any appear relevant to the crime. Once they narrow the field to a few devices they think belong to suspects or witnesses, Google reveals the users’ names and other information.
‘‘There are privacy concerns that we all have with our phones being tracked — and when those kinds of issues are relevant in a criminal case, that should give everybody serious pause,” said Catherine Turner, a Minnesota defense lawyer who is handling a case involving the technique.
Investigators who spoke with The New York Times said they had not sent geofence warrants to companies other than Google, and Apple said it did not have the ability to perform those searches. Google would not provide details on Sensorvault, but Aaron Edens, an intelligence analyst with the sheriff’s office in San Mateo County, Calif., who has examined data from hundreds of phones, said most Android devices and some iPhones he had seen had this data available from Google.
The site of the shooting in Avondale, a Phoenix suburb. Alex Welsh for The New York Times
In a statement, Richard Salgado, Google’s director of law enforcement and information security, said that the company tried to “vigorously protect the privacy of our users while supporting the important work of law enforcement.” He added that it handed over identifying information only “where legally required.”
Mr. Molina, 24, said he was shocked when the police told him they suspected him of murder, and he was surprised at their ability to arrest him based largely on data.
“I just kept thinking, You’re innocent, so you’re going to get out,” he said, but he added that he worried that it could take months or years to be exonerated. “I was scared,” he said.
Austin investigators obtained another warrant after a fourth bomb exploded. But the suspect killed himself three days after that bomb, as they were closing in. Officials at the time said surveillance video and receipts for suspicious purchases helped identify him.
An F.B.I. spokeswoman declined to comment on whether the response from Google was helpful or timely, saying that any question about the technique “touches on areas we don’t discuss.”
Officers who have used the warrants said they showed promise in finding suspects as well as witnesses who may have been near the crime without realizing it. The searches may also be valuable in cold cases. A warrant last year in Florida, for example, sought information on a murder from 2016. A Florida Department of Law Enforcement spokeswoman declined to comment on whether the data was helpful.
The approach has yielded useful information even if it wasn’t what broke the case open, investigators said. In a home invasion in Minnesota, for example, Google data showed a phone taking the path of the likely intruder, according to a news report and police documents. But detectives also cited other leads, including a confidential informant, in developing suspects. Four people were charged in federal court.
According to several current and former Google employees, the Sensorvault database was not designed for the needs of law enforcement, raising questions about its accuracy in some situations.
Though Google’s data cache is enormous, it doesn’t sweep up every phone, said Mr. Edens, the California intelligence analyst. And even if a location is recorded every few minutes, that may not coincide with a shooting or an assault.
Google often doesn’t provide information right away, investigators said. The Google unit handling the requests has struggled to keep up, so it can take weeks or months for a response. In the Arizona investigation, police received data six months after sending the warrant. In a different Minnesota case this fall, it came in four weeks.
But despite the drawbacks, detectives noted how precise the data was and how it was collected even when people weren’t making calls or using apps — both improvements over tracking that relies on cell towers.
“It shows the whole pattern of life,” said Mark Bruley, the deputy police chief in Brooklyn Park, Minn., where investigators have been using the technique since this fall. “That’s the game changer for law enforcement.”
Location data is a lucrative business — and Google is by far the biggest player, propelled largely by its Android phones. It uses the data to power advertising tailored to a person’s location, part of a more than $20 billion market for location-based ads last year.
In 2009, the company introduced Location History, a feature for users who wanted to see where they had been. Sensorvault stores information on anyone who has opted in, allowing regular collection of data from GPS signals, cellphone towers, nearby Wi-Fi devices and Bluetooth beacons.
People who turn on the feature can see a timeline of their activity and get recommendations based on it. Google apps prompt users to enable Location History for things like traffic alerts. Information in the database is held indefinitely, unless the user deletes it.
“We citizens are giving this stuff away,” said Mr. Ernsdorff, the Washington State prosecutor, adding that if companies were collecting data, law enforcement should be able to obtain a court order to use it.
Current and former Google employees said they were surprised by the warrants. Brian McClendon, who led the development of Google Maps and related products until 2015, said he and other engineers had assumed the police would seek data only on specific people. The new technique, he said, “seems like a fishing expedition.”