Why Did Chicago Shoot Down ShotSpotter?

ShotSpotter is an acoustic gunshot-detection system marketed by the public-safety technology firm SoundThinking and used by well over 100 cities in the U. S.  In some ways, it sounds like a law-enforcement dream come true.  Before ShotSpotter, a citizen who reported hearing gunshots could report them, but usually had no idea where the sound came from.  In an area covered by ShotSpotter, police can now often pinpoint the source of the gunshot with an accuracy in the range of 2 to 8 meters (about 6 to 26 feet).  What's not to like about ShotSpotter?

 

A lot, it turns out, at least if you're the mayor of Chicago.  Back in February, the office of Mayor Brandon Johnson, who won his first election campaign promising to end the use of ShotSpotter, announced that the city would not renew its ShotSpotter contract.  Understandably, having spent millions of dollars on the system, Chicago Police Superintendent Larry Snelling defends ShotSpotter.  He was quoted in an Associated Press report as saying, "If we're not utilizing technology, then we're falling behind in crime fighting." 

 

Mayor Johnson and other critics have three main charges against the way ShotSpotter is used.  They say it's "inaccurate."  That is of course a relative term.  In a technical paper published on the ShotSpotter website, the location accuracy was tabulated in a simulated test in a typical environment, with the results cited above (2 to 8 meters, typically).  With regard to false positives (saying there was a gunshot when there was actually some more benign sound such as a car backfiring) and false negatives (missing a true gunshot), the company claims that typically 96% of gunshots are detected correctly.  So although no system is perfect, ShotSpotter engineers seem to have achieved a remarkable success rate in a highly challenging acoustic environment by using advanced signal-processing techniques to enhance the accuracy of what is basically a time-of-flight location system. 

 

Another accusation leveled against the system as typically deployed in an urban setting is that it is racially biased.  A survey by Wired Magazine based on a leaked document giving the secret physical locations of about 25,000 ShotSpotter sensors backs up this accusation.  Wired found that about three-fourths of the neighborhoods where at least one ShotSpotter sensor was deployed were non-white, with an average income of about $50,000 a year.

 

When confronted with these results, SoundThinking senior vice president of forensic services Tom Chittum said that given a limited number of sensors, the company chooses to deploy them in areas that are "likely disproportionately impacted by gun violence."  In other words, they place sensors where they are most likely to pick up gunshot sounds.  For reasons that have nothing to do with ShotSpotter but are deeply rooted in historical and cultural factors, these neighborhoods tend to be poorer and where minority groups live. 

 

The third accusation is harder to refute:  that law-enforcement personnel "misuse" the data provided by ShotSpotter.  Critics cite cases in which police officers are deployed to a Shotspotter-indicated location and find bystanders who they then arrest and charge with violations unrelated to gun use.  Sometimes this leads to cases such as a Chicago grandfather arrested after a ShotSpotter location led officers to him, in which the accused was later released after a judge found insufficient evidence to convict him.

 

Undoubtedly, ShotSpotter has also assisted in the capture and conviction of real criminals.  Otherwise it seems hard to believe that police forces all over the country would spend hundreds of millions of dollars on it, unless they are all playing keep-up-with-the-Jonesville-police-department and making sure they have the latest technology just because it's there. 

 

In the case of Mayor Johnson dumping Chicago's ShotSpotter system, there has been no love lost between the mayor and the police force in general.  In April, Chicago's Fraternal Order of Police—their union—endorsed a drive to recall Mayor Johnson.  And in numerous ways, Mayor Johnson has made it no secret that he is highly critical of how the police do their job.

 

Not everyone in a neighborhood plagued by drug abuse, crime, and violence dislikes the police.  Lots of ordinary citizens would like to see more of the police than they do, and they are probably in favor of anything which helps the police do their job of fighting crime, including ShotSpotter.  After all, most of the sensors are on private property, and the owner's permission has to be granted for the sensor to be installed.  If there was a groundswell of opposition to ShotSpotter, you would think the company would have problems installing their sensors.

 

One of the most basic functions of a city's government is law enforcement.  But over the past few years, especially during the George Floyd riots of 2020, we have been treated to the spectacle of supposedly responsible officials proposing to defund entire police departments.  In the cities where movements in that direction actually gained headway, the results were in keeping with what common sense would predict:  soaring rates of crime and an exodus of both residents and businesses. 

 

District attorneys who make blanket announcements that certain types of crime will no longer be prosecuted find that those exact kinds of crimes proliferate.  How this policy is supposed to benefit society (unless you consider "society" to be restricted to the class of petty criminals) is not clear.

 

As a technology, ShotSpotter works about as well as the state of the art permits, given the challenging environment it works in.  But technology is always about more than technology.  The social environment and the way ShotSpotter results are used has led to a perception in some circles that it is just another way to beat down black people and other persecuted minorities.  Many police personnel are of the same race and culture of the people they are sworn to defend.  It is profoundly demoralizing to be told that a dangerous, tedious job which you do to the best of your ability is not only not appreciated by the highest official of the city, but actively criticized.  With regard to law enforcement and the use of ShotSpotter, Chicago is clearly a house divided.  And we know what happens to a house divided sooner or later:  it cannot stand.

 

Sources:  The Wired report on ShotSpotter sensor locations was published on Feb. 22, 2024 at https://www.wired.com/story/shotspotter-secret-sensor-locations-leak/.  I also referred to the Associated Press article "Chicago to stop using controversial gunshot detection technology this year" at https://apnews.com/article/shotspotter-chicago-gunshot-technology-mayor-f9a1b24d97a1f1efb80296dbe9aff1ed.  I referred to ShotSpotter Inc.'s technical note TN-098, "Precision and accuracy of acoustic gunshot location in an urban environment," dated Jan. 2020.

 

Synthesia: A Skateboard or a Crutch?

 

Last week, my wife and I joined some friends for supper at an unpretentious cafe in a nearby town.  It's the kind of place where the waitresses learn the customer's names and most people don't need to look at the menu before they order.  We've eaten there numerous times, and the food was good, as usual.

 

But since the last time we visited the place, something new had been added:  a small white electronic piano taking up a few feet of lunch-counter space, just as you came in the main door.  Seated at the piano was a teenage boy, and he was playing pop tunes.  I regret to say I can't remember what any of them were, but as we sat down close by, we had no trouble at all hearing what he was playing.

 

There was something off about his style, but I couldn't put my finger on it.  The base line sounded rather mechanical, and while there was a melody there wasn't much harmony with it, if any.  Still, you could recognize the tune, and while I didn't think this particular live music was much of an addition to the atmosphere, it wasn't cringingly bad, either.

 

Halfway through the meal, my wife, who was seated with a better view of the pianist, told me he wasn't using sheet music.  There was something on his smartphone that he was using instead.  I turned around to look.

 

On the kid's screen was a pattern of vertical dashes moving upward, and below the dashes was a small video of two hands moving around on a keyboard, playing the tune he was playing.  Older readers may be familiar with the concept of a player piano.  Before the days of high-quality sound recording, mechanical self-playing pianos were developed that used wide stiff-paper rolls with holes punched in them, and a device called a trackerbar read the hole patterns pneumatically as the roll unwound past the bar and the piano played in accordance with the pattern. 

 

Here was a piano roll, in digital form.  But instead of a player piano, there was a human piano player playing the part of a player piano trackerbar. 

 

After we finished the meal, I went up to him, dropped some money in his tip jar (which was already well stocked), and asked him what was on his smartphone.

 

"It's a YouTube video.  See, all I have to do is follow the keys.  I've taught myself.  It's easy."

Keeping up with the moving dots seemed like an impossible task to me, but then again, I was a little older than he was (he told me he was 16). 

 

A little research shows that the program which produces the piano-roll patterns is a video game called Synthesia.  I found a long Reddit thread in which various people chimed in on whether using Synthesia to play piano music was good, harmful, a waste of time, or what.

 

As is usually the case with these kinds of Internet debates, opinions are divided.  Most of the commenters came down on the negative side of using Synthesia exclusively.  One said, " . . . you probably won't find anyone using them if they're really good at piano, because learning from synthesia gets significantly harder the harder the songs get." 

 

On the other hand, one enthusiast said, "I'm very pro [synthesia].  I have memorized Maple Leaf Rag, Fur Elise, and currently working on a very advanced piece.  I'm an adult beginner and piano is not a huge priority in my life.  I don't really want to learn to play the 'right' way.  I just want to go straight to playing cool pieces."

 

The fact that conventional musical notation is essentially a foreign language that one has to learn came up a lot.  A person who could read music and also uses Synthesia-based videos says that he picks up non-classical music with Synthesia, although he usually knows the piece already from having learned it from sheet music.

 

While I was secretly hoping to find some manifesto by the Piano Teachers' Guild coming out with guns blazing to condemn Synthesia, there is apparently no such document.  Instead, several online commenters say it can be good for beginners, but definitely no substitute for learning to read sheet music the old-fashioned way. 

 

It wouldn't surprise me at all to learn that back when player pianos became available around 1900, some people taught themselves to play by watching the holes pass over the trackerbar.  But the only role player pianos played in the life histories of famous musicians I'm aware of, were as ways of preserving their playing at a higher quality than old sound-recording technology could achieve.  For example, George Gershwin produced a set of reproducing-piano rolls which preserve dynamics of playing as well as timing and sequence.  He was even known to go over the rolls after he had recorded them to touch up mistakes and otherwise enhance his own performances.

 

So are the piano teachers of the world doomed by the advent of Synthesia and its spawn of YouTube videos?  It doesn't look that way. 

 

For people who either can't afford piano lessons or aren't that committed to learning, but would like to do something musical with an inexpensive keyboard and a smartphone, Synthesia seems to be a good way to fool around with the basics.  In that sense, it's kind of like using a skateboard instead of walking.  It's fun, it will get you some places faster, but nobody skateboards from Nashville to Chicago.  And for people who simply can't imagine trying to learn to read musical notation but want to make music with a keyboard, it's a crutch that might enable you to do what you otherwise couldn't do at all.

 

Sources:  The Reddit thread from which I excerpted comments can be found at https://www.reddit.com/r/piano/comments/11j3u6o/i_dont_understand_how_people_learn_a_song_using/.  I also referred to the Wikipedia article on Synthesia.