As Americans grow increasingly anxious about the scope of government spying, a recent report brought the issue close to home, confirming those fears about privacy having become a quaint, archaic notion.

TV station ABC News10 learned that at least nine Bay Area public agencies—including the San Jose Police Department (SJPD)—use a controversial surveillance system that mines real time phone data.

Stingrays, as they’re commercially called, act like a cell tower to scoop up untold amounts of phone data by pulling all wireless devices in range into the same network.

News10 reporter Michael Bott says his team put in records requests to dozens of government agencies in Northern California last year. Many got denied. The investigation fits into a broader national project by parent company Gannett.

SJPD spokesperson Sgt. Heather Randol told News10 and San Jose Inside that she won’t comment on the technology, though her employer was one of the nine local agencies to supply records to the Sacramento news station.

Those records show that San Jose secured a $500,000 federal grant to buy the technology in 2012 after conferring with surrounding agencies about the efficacy of this type of surveillance. In grant applications, the city talks about how it would be able to coordinate phone data with law enforcement in Oakland, San Francisco, Sacramento, Los Angeles and San Diego to speed up police work.

Heavily redacted purchase orders show SJPD used Stingray surveillance in 2013, though it’s not clear whether any arrests were made based on the information it collected.

The money to buy the technology was pegged for anti-terrorism efforts, but reports say Stingrays have become part of routine police work. Critics of the practice call it “mission creep,” which is when authorities justify data collection for one reason but ultimately use it for another purpose.

San Jose Inside spoke to Electronic Frontier Foundation (EFF) attorney Hanni Fakhoury to learn more about this type of surveillance:

SJI: What type of information can authorities glean using this technology? Can they literally hear us or do they look at just metadata? Although, even if it’s just metadata, a recent Stanford study has shows just how much one can piece together about a person’s life without ever eavesdropping on conversations.

HF: Its not entirely clear what is gathered through the use of the Stingray, because both the police departments and Harris, the company that makes [the technology], are very secretive about the devices and resist efforts to gain information. At a minimum, we know they can capture a person's location by identifying which specific phones connect to the Stingray and then determining its approximate location. We also know they can be configured to capture the actual conversations themselves, though there have been assurances they aren't being used for that purpose. But the assurances are simply that. There's been no explanation of why that is so. Is it because Harris won't configure the technology to do that in the devices they sell to police? Is it because that option is turned off and can't be turned on? It’s unclear.

Do police need a warrant to snoop on our call information?

Well, it depends on what the police are gathering through these devices. If they're capturing everyone's information in a wide vicinity, I actually don't think even a search warrant would allow the police to do that because it wouldn't be particular, meaning targeted and narrowed towards a specific person. If they're using it to capture information about only a specific target, we think they need a warrant to use the device. Courts haven't dealt with the issue directly, because the use of the device has been secretive.

A lot of the money used to pay for [Stingrays] comes from federal anti-terrorism grants. Is it in any way illegal to then use the technology to conduct routine police work? What about in gang-related cases? Could that somehow be construed as domestic terrorism that merits surveillance technologies like this?

I am honestly unsure about whether it violates any conditions attached to the distribution of grant funds. But it seems a bit disingenuous to claim something is needed for terrorism and national security and then to use it for garden-variety police work. I don't think gang-related investigations qualify as domestic terrorism that merits this kind of surveillance technology.

In what cases do you believe it appropriate to leverage this technology?

Again, I think general broad requests sucking up everyone's data is never appropriate. And I think that using a technology like this at something like a political protests has the potential to chill the First Amendment right to free speech and protest. It may be appropriate in a targeted investigation provided police get a search warrant and are being forthright with the court about what it's doing, something we've seen be a problem before in Northern California.

What worries you about Stingray? We've seen it challenged in some court cases as unconstitutional, as in this instance. Your thoughts?

The worry with Stingrays is they enable the police to gather large batches of communication records from people who just happen to be in a particular place where police activity is occurring, even though they haven't done anything wrong. That is precisely what the Fourth Amendment is designed to prohibit. Plus beyond the technology itself, as we've seen, there's too much secrecy about police use of them. The federal cases in San Francisco referenced in the SF Weekly article all involve the same basic allegation: that police and prosecutors are not being forthright with criminal defendants, judges and the general public about the use of these devices. That is problematic in functioning democracy.

What do you think the general public should do to protect themselves?

They should understand the technology and take steps to protect their privacy by perhaps turning off their phone if that's a realistic option (as someone glued to his phone, I know it's a tough thing to do). Most importantly, they should demand accountability. We've seen in Oakland what happened when the public spoke out against the Domain Awareness Center (DAC). We need the public in cities with these devices to start asking tough questions of their public safety officials.