NYPD's New Gunshot Detectors Record More Than Just Gunshots

ShotSpotter has successfully reduced police response time to crimes, but has little oversight in New York City.


Last week, New York City Mayor Bill de Blasio and NYPD Commissioner William Bratton announced the launch of ShotSpotter, a network of sensors that can pinpoint the exact location of a gunshot, which will be deployed in several high crime areas in the Bronx and Brooklyn. Bratton declared, "This gunshot detection system is going to do a world of good in terms of going after the bad guys."

Big Brother is Listening
Foter/Nicholas Eckhart

There's strong evidence suggesting Bratton is correct. As Reason's Jim Epstein reported, ShotSpotter helped contribute to bringing crime-plagued Camden, NJ's "average 911-response time (down) from one hour to 90 seconds." Providing law enforcement with accurate information about crimes in progress is a far better use of resources than earlier systems that had cops stopping-and-frisking anyone in the vicinity of a shooting who roughly matched the description of a suspected perpetrator. 

But there are growing concerns about how information recorded by ShotSpotter can be stored and used, particularly in New York City, where the City Council has yet to pass any legislation regarding oversight of the recorded material. Though, according to Fusion.net, Public Advocate Letitia James "has introduced a bill to the city council to require quarterly reports on the data." 

ShotSpotter's website claims its microphones are not triggered by, "car doors slamming, people yelling "bang bang!", loud music, airplane engines, leaf blowers, cheering, highway noise, car engines revving, drag races or tires squealing," but WNYC reported that since 2010 in Newark, NJ, "75 percent of the gunshot alerts have been false alarms."

This is important because when ShotSpotter is triggered, it captures a few seconds of sound before and after the triggering moment. Though the microphones are as high as 100 feet above the ground, they have the ability to pick up intelligible conversations, which have been deemed admissible in court as part of several criminal cases around the country. In these cases, ShotSpotter has apparently contributed to solving violent crimes. But some civil libertarians are pushing back on handing the government a blank check to record incriminating conversations in public and use them to prosecute.

TakePart.com quotes Jay Stanley of the ACLU's Speech, Privacy and Technology Project as saying, "We are always concerned about secondary uses of technology that is sold to us for some unobjectionable purpose and is then used for other purposes."

We're not quite London yet, but ensuring police departments and city governments are transparent and limited in the scope of their use of ShotSpotter must be a priority for those who still value a free and open society. As my colleague Jim Epstein wrote, "It's incumbent on local police departments to be more open about how they're using the data they're collecting and to invite independent monitors to oversee their internal procedures."

Transparency will help ensure public confidence that the government is truly serving the interests of public safety, and not simply casting an indiscriminate surveillance net on anyone who dares to speak in public. 

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  1. Right. A billion dollars worth of technology will be deployed in order to help police make their “ex post facto” arrival more time-efficient….

    …. so that they have more time to document the scene of the crime, take pictures, take statements, and other things which have zero to do with “crime prevention”

    “ShotSpotter helped contribute to bringing crime-plagued Camden, NJ’s “average 911-response time (down) from one hour to 90 seconds”

    911 response? You mean the ‘crimes that people phone in’? the best ubiquitous sensor-technology can offer is ‘improved response to citizen-initiated reports’?

    Also = speaking of that crime-fighting revolution in Camden…. they had ~3X the national average in crime in 2000… and in 2012? slightly more than that.

    Murders also more than doubled. But hey! They have great data on where the shootings happened.

    1. Thanks for the 911 snark — I was going to mention that myself. If 3/4 of the shotspotter alerts are false alarms, are the cops waiting for 911 calls to know which ones to respond to? Gosh that is useful!

      1. I don’t see a problem with this. It sounds like the previous status quo was that a shooting would occur, someone would call it in and then the cops would spend 3600 seconds searching a large area because the caller only heard it but didn’t witness it.

        Now it sounds like the situation is that when someone calls in a shooting the cops can just query their database and immediately see where the shooting occurred. (And they ignore any hits in their database that do not correlate in time with a reported shooting).

        In this case the cost of a false alarm is very low, but the cost of a missed true alarm is very high. So you’d want to tune the thing so that you get all the true alarms even if you end up getting a lot of false alarms too. Seems reasonable to me.

  2. Transparency and the NYPD – or any other government agency? I guess hope does spring eternal.

  3. “…they have the ability to pick up intelligible conversations, which have been deemed admissible in court…”

    I only read the link to the Contra Costa Times but that was a recording of “deathbed testimony” by a victim and was actually set off by a gunshot. A gunshot that, according to the victim’s recorded voice, was fired by the guy that was charged with murder.

    If the argument is that these could be just turned into ubiquitous conversation recorders, I get the point. But when it records an actual crime being committed, I fail to see its inadmissability.

  4. So what exactly have the courts been saying, that people don’t have a resonable expectation of privacy when conversing in public?

    1. I thought they said there is no expectation of privacy anywhere, at all.

      1. Last I checked, the law that still applies is Katz … which has a pretty kooky test for what can be determined “reasonable expectation”

        “IF a person did not undertake reasonable efforts to conceal something from a casual observer (as opposed to a snoop), then no subjective expectation of privacy is assumed.[14]

        The second part of the test is analyzed objectively: would society at large deem a person’s expectation of privacy to be reasonable? If it is plain that a person did not keep the evidence at issue in a private place, then no search is required to uncover the evidence.”

        The examples typically given are, ‘when a person uses a phone booth*, they are assuming that there is privacy even though anyone could stand next to it an eavesdrop. Whereas there is no such expectation for things people threw in the trash…

        (*anachronism; see ‘Dr Who’, Superman)

        1. phone booth? Nowadays you’d have to go outside and around walk a bit away from the entrance before you had an expectation of privacy.

    2. If I were on a jury where that was deemed admissible even though it is clearly a violation of the Fourth Amendment, what would happen to me if I refused to vote guilty?

      1. nothing… you might get a stern lecture from a judge. Jury nullification is a viable defense.

      2. Theoretically nothing. Jury nullification scares the crap out of judges and prosecutors precisely because a jury’s deliberations are confidential and there isn’t much of anything they can do to stop it.

      3. Your fellow jurors would probably beat on you until you agreed if you were keeping them from going home early.

        1. unless they were unemployed and enjoyed the local sandwich shop for free lunch.

      4. you wouldn’t be on a jury if you thought that. the prosecutors will make sure of that.

  5. But some civil libertarians are pushing back on handing the government a blank check

    Government already has the blank check. We’re just trying to keep tabs on what they’re spending it on.

  6. it captures a few seconds of sound before and after the triggering moment.

    How is recording before it is triggered? Does it record all the time and just stores sounds that are within certain time frames before and after it is triggered?

    1. That’s my guess. I seems to be the only thing that makes sense.

    2. It must record all the time. The question is how much it keeps. If it’s just a twenty second loop, then I don’t see how that’s a big deal. Now if it stores everything, well that’s just creepy.

      1. let’s assume that the government opted for the “just creepy” option.

        I can see the sales pitch now.

        “We have the common sense option…”
        “NO, what’s the creepiest package you’ve got?”
        “Well, we do have the ‘just creepy’ package.”

      2. It must record all the time.

        If that’s the case, then “we only keep a few seconds before and after” is almost certainly a lie.

        1. Could be like a flight data recorder which runs on a loop.

          1. It’s probably this. Recording constantly means either high data rates or lots of storage space. This is also how a lot of dashcams work. They record on a loop until you hit the “something interesting happened” button. Then they save the previous X minutes and continue saving everything after until you hit the “interesting stuff stopped happening” button.

    3. I’d like to say the “before” is a mistake in the description of the technology. But it probably DOES make it awfully attractive selling point when government is your client.

    4. Looking through the website doesn’t give much info on how the actual recording takes place, but if I had to guess it continuously records to a cache and records over it when the cache is full. When the system is triggered by what it thinks is a gunshot, it grabs a certain amount of the cache before and after the event and sends it to the dispatch. It doesn’t look like there is any permanent storage on the device.

  7. anyone in the vicinity of a shooting who roughly matched the description of a suspected perpetrator

    So, any dark-skinned youth wearing a hoodie, amirite?


    1. It was God’s plan that Zimmerman shoot Trayvon Martin. Maybe the NYPD is also privy to God’s wants and needs…

      1. Speaking of Zimmerman….

        He’s now bitching about Obama

        I’m not sure what they guy is going for here. You’d think he’d have been hoping for the world to forget him ASAP.

        1. He’s probably figured out that he won’t be forgotten until Shapton is dead and buried, and decided to just go with it.

        2. Maybe he went a little crazy from the whole experience… or was already a little crazy to start with. Yeah, you’d have to be a little crazy to join the neighborhood watch…

  8. We’re not quite London yet

    In Manhattan, we might as well be. I see the damn things everywhere, though I have to admit I have never seen them clustered in sinister bunches like in some of the London photos.

  9. 75 percent of the gunshot alerts have been false alarms.

    And how many of the remaining 25% turned out to be shots fired in self-defense?

    1. This is New York we’re talking about. They don’t recognize a right to self defense. You have a right to hire government approved bodyguards, if you can afford them.

  10. they ban law abiding citizens guns, criminals still have them, so now they set up an eaves dropping system to listen in on every bodys conversations..

  11. And the commissioner suggested anyone concerned about privacy should “get a life”! I guess he is not being honest about the capabilities of recording people or “eavesdropping”. I hope he was being just as “transparent” when he said that the police would be using more force in their upcoming interactions with perps!

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