Are you familiar with the Shotspotter system? I’d seen it on a National Geographic TV show, and remembered in the back of my head reading about it being deployed in parts of Boston. It’s actually very cool how it works — it essentially has a big array of microphones, and when it “hears” a gunshot, it’ll compare the exact time of arrival of the sound at each location to triangulate a position, which then pops up on a dispatcher’s screen.

So I’m listening to Boston PD on the radio, and maybe five minutes ago the dispatcher called out for a reading on the ShotSpotter system. “Five, six, seven, looks like eight shots fired.” She figured out the location from the map (apparently, an alley), and started a couple cars. In maybe 60 seconds an officer was on the scene, reported a car leaving, and had confirmed that shots were fired with a witness.

About a minute later, the dispatcher said that they had received a 911 call for shots fired from the same location. (Which means that they had an officer arriving on scene by the time the call came in!) They’ve just pulled over a possible suspect, and another officer found the shell casings. Detectives are en route now for forensics processing.

I’ve got to say, this seems like a pretty impressive system.

4 thoughts on “ShotSpotter

  1. Hi, Matt. James from ShotSpotter here. Thanks for your excellent post! (The NatGeo piece is pretty cool, isn’t it? LA has been using our stuff since 2001/2002.)

    Although I’m not familiar with the incident you wrote about, I can confirm that you’re absolutely right: in most cases we get a notice and location to police long before they get a 911 call (if they get one at all). We calculate the location within a few seconds (it takes a few seconds for the sound to travel from the gun, and then we need a few seconds to do the math and filter out the other noises) and police have the data within 10-15 seconds of the trigger being pulled. Cases such as this one are particularly gratifying, because they point out the real benefit: accurate information *before* the 911 call. (Bear in mind that many 911 callers, even though they mean well, can be as far as a half mile away, and therefore can’t really tell police where precisely to go.) It’s sad, but in some cities, we hear about four *times* as much gunfire as gets called into 911 (although Boston is *not* one of those cities). Incidentally, if the vehicle had been moving (i.e., if this had been a “drive by” shooting), we would probably have reported the speed and direction of the vehicle, which of course can also be really useful for responding officers.

    Thanks for catching this and for the post! It’s particularly cool to know that we helped get police to the scene quickly in this case.


  2. You’ve got to love the power of the Internet!

    It’s sad, but in some cities, we hear about four *times* as much gunfire as gets called into 911

    That statistic is quite disturbing! I’d like to think it would be the other way — multiple calls coming in for each shot heard.

    Incidentally, if the vehicle had been moving (i.e., if this had been a “drive by” shooting), we would probably have reported the speed and direction of the vehicle, which of course can also be really useful for responding officers.

    Yikes! Could the system possibly get any cooler? 😉

  3. Matt,

    Regarding the 911 under-reporting: it really *is* disturbing, that’s for sure. There is some sociological sense to all of it, which is sad but understandable: there tends to be somewhat higher 911 reporting (multiple reports on single incidents, higher percentage of incidents reported) in cases when someone is physically injured or killed (this makes intuitive sense) and in relatively lower crime areas. The latter tendency–lower crime (= safer) areas having higher reporting percentages–is disturbing but logical: people tend to get inured to the sound of gunfire if they hear it every evening. On the other hand, if they hear it once a year, they’re likely to call the police when they do. Unfortunately, this results in a confusing demographic picture of gunfire rates: the 911 statistics produce somewhat “leveled” demographics, with higher crime areas having lower reporting rates (and therefore appearing to have lower gunfire rates) and lower crime areas having higher reporting rates (and therefore appearing to have higher gunfire rates, even if those rates are still lower than in the higher crime areas).

    There’s some really interesting sociological research out there which supports the idea that people “get used” to certain types of “low level” crime and stop reporting it. (It’s very sad, because of course it’s local residents who are most likely to be able to take control of their neighborhoods and to help police keep them safe.) The main body of research in this area goes under the rubric of the “Broken Windows Theory” (, on the eponymous book). A lot of gunfire doesn’t actually hit anyone (the numbers vary, but we have seen cities where only 10% of gunfire injured a person), but it *does* produce a sense that crime is uncontrolled. (Note: I’m not talking about hunting or other legal gun uses. We’re pretty much only deployed in places where shooting a gun is illegal.)

    The flip side of this, and the part I’m personally most excited about, is that there are a number of communities where people are actively lobbying for the use of technologies such as gunshot location because it can help combat a sense of general lawlessness. East Palo Alto, California, for example, has been very vocal, as have community activists in Washington, DC. This is particularly true because when gunfire doesn’t actually hit anyone it appears to be used as something of a psychological/intimidation tool, and therefore there’s even more room for communities to take charge and put a stop to it.

    Thanks again for your post–it’s great to see people focusing on this. Gun violence is a huge problem, and the more of us paying attention to it, the more we’ll be able to combat it.


  4. Matt,

    One last comment. There are a lot of ways that communities can get aggressive about combating gun violence. As a guy running a business, of course I want people to think about ShotSpotter. But there are also some excellent community-based approaches that have a lot of merit. Two of my favorites are, both sponsored by the same parent organization, are:

    ASK (, a program which encourages parents to ask the parents of their children’s friends whether they own guns which their kids might get their hands on.

    and, particularly on my mind these days amidst more and more school shootings:

    Speak Up! (, which provides a hotline and resources for kids who hear friends talking about brining a gun to school (or god forbid using it).


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