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ShotSpotter: listening in on the neighborhood

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Re: ShotSpotter: listening in on the neighborhood

#131

Post by photochemsyn »

Aurornis wrote: post #65
loteck wrote: post #46

I would request that a crowd as technically sophisticated as HN move past marketing claims when discussing this system. "Gunshot detection" is pure marketing. The devices are hot mics — public audio surveillance. The software layer triggers alerts on loud noises, which are sent off to a facility that is little more than a call center, for characterization by a human worker there. This system detects door slams and po…

> This system detects door slams and popped volleyballs just as well as it detects gun fire (which is to say, imperfectly on all counts). Sound classification moved far beyond what you’re claiming years ago. If you set the threshold at “imperfectly” then no system will ever meet your bar, because perfect is an unreasonable threshold. However, the claim that we’re unable to differentiate between gunshots and car doors…

Sound classification under fairly well-controlled conditions could be very different from a real world streetcorner situation, where sound can bounce off surfaces and generate different signals depending on direction and distance of origin relative to the collecting microphone. High-quality omni-directional microphones can be expensive and I imagine there would be theft concerns if they used really good ones.

Re: ShotSpotter: listening in on the neighborhood

#133

Post by jacurtis »

verteu wrote: post #116
jcrawfordor wrote: post #71

Hello all, occasionally I write what I consider "Albuquerque content" and I do not expect it to become broadly popular. This article is something I put together very quickly and it probably assumes a certain degree of familiarity with the political context around policing in Albuquerque (which either side will tell you is very contentious) and, more broadly, policing and civil justice. Even without the currently evol…

Why didn't you mention that the only "conversation" recorded by ShotSpotter admitted in court was a guy saying "[shooter's name], why did you shoot me!" two seconds after the sound of gunfire? It seems an important piece of context if you are concerned about surveillance.

Yes it is very important. Shotspotter is like a DVR. It's always "recording", but it is running on a very very short recording loop.

The detection of gunshots is based on an algorithm. When triggered, it saves a few seconds before the sound and several seconds afterward.

It is different than police just being able to pull up the recordings for a certain street corner from 2 weeks ago or even a day ago and listen in on people's conversations. The case in question came from a shotspotter recording gunshots, and the short clip also happened to include speech within it since it directly followed the sound of shots.

Re: ShotSpotter: listening in on the neighborhood

#135

Post by [deleted] »

Aurornis wrote: post #73
bombcar wrote: post #8

Earlier quoted context omitted.

It sounds like shotspotters are likely to be near where shots are; and that the wealthier you are the more likely you’d NOT want to be where the shots are.

Putting surveillance for gun crime in areas with the highest rates of gun crime is obviously what’s happening. I think the author and some commenters are nervous about claims that gun crime is inversely correlated with neighborhood wealth, which creates some of these strange accusations that some other bias is at play. If you pull up a map of crime in most cities the inverse correlation with home prices is obvious. I…

[deleted]

Re: ShotSpotter: listening in on the neighborhood

#137

Post by jcrawfordor »

jacurtis wrote: post #133
verteu wrote: post #116

Earlier quoted context omitted.

Why didn't you mention that the only "conversation" recorded by ShotSpotter admitted in court was a guy saying "[shooter's name], why did you shoot me!" two seconds after the sound of gunfire? It seems an important piece of context if you are concerned about surveillance.

Yes it is very important. Shotspotter is like a DVR. It's always "recording", but it is running on a very very short recording loop. The detection of gunshots is based on an algorithm. When triggered, it saves a few seconds before the sound and several seconds afterward. It is different than police just being able to pull up the recordings for a certain street corner from 2 weeks ago or even a day ago and listen in o…

ShotSpotter's own public statements say that audio is retained for 30 hours, see e.g. https://www.soundthinking.com/faqs/shotspotter-privacy-faqs/. In the past they provided Albuquerque with a document that said 72 hours, but I believe they have been reducing that period over time. It may also depend on their specific contract with the law enforcement agency. Still, we know that they must retain recordings, because they do take requests from customers to reanalyze data that did not result in an alert.

For convenience, the most relevant text: "If the system misses a gunfire incident, police may contact the company to see if there is any audio or location evidence. In this case, only authorized ShotSpotter personnel with proper credentials can access sensor audio to search. Their search is limited to the 30- hour sensor storage timeframe."

ShotSpotter used to have significantly fewer privacy protections, and retention was indefinite early in the product's life. Fortunately, a combination of legal challenges and statutory privacy policies among their customers have lead to them significantly improving their privacy controls over time.

Re: ShotSpotter: listening in on the neighborhood

#138

Post by jakelazaroff »

Aurornis wrote: post #73
bombcar wrote: post #8

Earlier quoted context omitted.

It sounds like shotspotters are likely to be near where shots are; and that the wealthier you are the more likely you’d NOT want to be where the shots are.

Putting surveillance for gun crime in areas with the highest rates of gun crime is obviously what’s happening. I think the author and some commenters are nervous about claims that gun crime is inversely correlated with neighborhood wealth, which creates some of these strange accusations that some other bias is at play. If you pull up a map of crime in most cities the inverse correlation with home prices is obvious. I…

> If you pull up a map of crime in most cities the inverse correlation with home prices is obvious.

If the police department spends the majority of its resources on certain areas, it will respond to the majority of incidents and make the majority of arrests in those areas. You can truthfully say "look, these numbers are higher than anywhere else!" but that doesn't necessarily mean there's more crime happening there — it could also mean the residents are overpoliced relative to other neighborhoods.

With regard to the article, why is it obvious that police are putting surveillance in areas with the highest rates of gun crime?

Re: ShotSpotter: listening in on the neighborhood

#139

Post by wl »

reaperman wrote: post #119
sixothree wrote: post #60

Earlier quoted context omitted.

This is entirely grotesque. But the systematic deception is especially appalling.

ShotSpotter has (used to?) manually changed the location of detected gunfire to placate police who needed the evidence to point to their primary suspect. Then they could go to court and say “this system showed the gunshots came from the suspect’s location”. But “the system” didn't show that, until ShotSpotter employees manually changed the data. They spent a lot of effort hiding that as well.

They don’t change the data. They change their interpretation of it. The police say the classifier got something wrong, so the classification gets updated, both for the record and to improve the classifier. The police say that the location is wrong. The company looks at the data, maybe finds that the system automatically located on an echo at one or more sensor and then recomputes the location using the primary pulse.

Re: ShotSpotter: listening in on the neighborhood

#140

Post by prophesi »

torstenvl wrote: post #122
prophesi wrote: post #118

Earlier quoted context omitted.

Hasn't that historically been the opposite? If a rich/white person is murdered, it's a headline-grabbing tragedy. Even serial killers are more likely to evade detection if their targets are minorities, though the reasons for that are more complicated than just systemic prejudice.

That's the point. Believing the things that would have to be true for GGGP's viewpoint to be even plausible , let alone true, requires a complete divorce from reality.

Gotcha! The comment parent of mine makes a lot more sense now.
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