‘ShotSpotter’ says mistakes are rare, but Detroiters want more transparency
Detroiters have received virtually no information on the accuracy of gunshot alerts from a private company hired two years ago by the city to scatter recording devices across neighborhoods.
SoundThinking, Inc. – formerly known as ShotSpotter – alerts the Detroit Police Department when gunshot sounds are picked up by its audio sensors. A key feature of the controversial surveillance technology, according to Police Chief James White, is its ability to pinpoint the location of shootings more reliably than witnesses who don’t always call 911 to report gunfire.
But residents, activists and police oversight officials argue it’s unclear how accurate the devices are without more detailed data. Critics have called for more accountability to justify spending $8.5 million from the city’s general fund on the technology. The Board of Police Commissioners is pushing the police department for greater transparency, arguing that it hasn’t received data that should be made public.
BridgeDetroit recently obtained an accuracy scorecard created by SoundThinking one year after submitting a June 2022 Freedom of Information Act request. The scorecard suggests SoundThinking alerts are rarely inaccurate, but activists who oppose the technology said an independent review is needed to verify what the company reported.
“Optimally, an independent city agency or third-party firm would (review) data to find the true number of false positives,” said Alejandro Navarrete, research and policy director for Detroit Action, a nonprofit social justice organization. “Long story short, our skepticism is the same.”
Molly Kleinman, managing director of the Science Technology and Public Policy Program at the University of Michigan, said the data BridgeDetroit obtained through FOIA doesn’t put accuracy concerns to rest. Kleinman said relying on DPD to flag inaccurate alerts means SoundThinking is only counting errors based on what police are able to prove.
DPD said in a statement to BridgeDetroit that the department holds ShotSpotter “to a high standard of accuracy that has been continually exceeded.”
BridgeDetroit requested accuracy data collected since the devices were first installed in two police precincts in March 2021. The FOIA request went unanswered for a year. Since then, the company changed its name from ShotSpotter to SoundThinking and City Council approved a $7 million contract to expand the listening devices to seven more police precincts across Detroit.
A two-page scorecard released to BridgeDetroit in June tallies the mistakes as required under SoundThinking’s contract with Detroit. The following statistics were recorded between 2021 and the first six months of 2022:
- Seventeen false positives, which occur when SoundThinking generates a gunfire alert for something that was later determined not to be gunfire.
- Eighteen false negatives, which occur when SoundThinking incorrectly determined a sound was not gunfire.
- Nine missed incidents, which occur when SoundThinking did not identify a percussive sound when shots were fired.
- Six mislocated incidents, which occur when SoundThinking detected a gunshot but mapped it in the wrong location.
The scorecard shows 99.6% of gunfire alerts were accurate in 2021 and 99.5% were accurate for the first six months of 2022. There were 7,188 gunshot alerts recorded between that time frame. Nearly 35,000 gunshots were identified by SoundThinking so far this year, with audio listening devices spread across a broader area of the city.
“ShotSpotter continues to be a valuable tool in helping the Detroit Police Department respond to and investigate shots fired incidents in the city, by quickly sending officers to the locations where shots are fired. DPD will continue to use all available resources to keep Detroiters safe,” DPD’s statement adds.
Detroit’s contract with SoundThinking requires the California-based company to accurately identify 90% of outdoor gunfire within its coverage area. White told BridgeDetroit weekly audits show the standard is being surpassed. The chief said evidence of gunshots are reliably located within an 82-foot radius of the alert.
“(A SoundThinking alert) takes us right to the point where the shot was fired; within those 82 feet we generally recover evidence,” White said in a May sit-down with BridgeDetroit. “If we don’t, it either didn’t happen there or someone collected evidence, but we still should be able to identify that something happened by talking to neighbors and things like that.”
Police Chief James E. White sits down with the BridgeDetroit newsroom on May 18, 2023. (Photo by Quinn Banks)
A DPD spokesman said police are responsible for notifying SoundThinking when mistakes are made. SoundThinking did not respond to a request for comment.
Detroit’s Board of Police Commissioners has not received quarterly reports tied to SoundThinking’s service as required under DPD policy, according to Board Secretary Victoria Shah. The civilian oversight body is supposed to receive the number of confirmed incidents, false detections, average response times to gunshot alerts and the number of guns, shell casings and arrests connected to gunshot alerts.
Weekly reports only include the number of shots detected and alerts issued in each police precinct. The police department hasn’t released data on the number of guns recovered this year, despite keeping track of that statistic in previous years. A DPD spokesperson said an “internal tracking issue” is to blame; the department is acquiring a data tool to process the information.
Shah said the lack of accuracy data makes it difficult for the board to work with DPD to navigate “possible civil rights infringements” that residents expressed concerns about. BOPC is working on policy changes that would require more detailed reports, and give the board power to publicly release gunshot detection system data.
“Whenever someone is controlling the data, they tell you what they want you to know,” said Police Commissioner Ricardo Moore.
But Willie Bell, another member of the Board of Police Commissioners, said he’s not concerned about inaccurate reports because “we make few arrests” connected to gunshot alerts. Bell said the alerts are a valuable tool to locate gunfire and collect evidence that can be used to aid police investigations.
Detroiters have called for an independent review similar to studies of SoundThinking’s use in Chicago. A 2021 report by the MacArthur Justice Center reviewed 21 months of SoundThinking alerts and found 86% of alerts led to no report of a crime. A similar study by Chicago’s Office Inspector General found only 9% of alerts uncovered evidence of a gun-related crime.
The devices cover 28 square miles of Detroit. When a gunshot sound triggers the sensor, the audio data is sent to SoundThinking audio analysts for review. An alert is sent to police after the sound is confirmed as a gunshot.
DPD policies require units that work with the technology to report false positives to the Crime Intelligence Unit.
SoundThinking’s contract with Detroit notes loud sounds like fireworks can be mistaken for gunfire. The company doesn’t count the 48-hours around New Year’s Eve and July 4 in its accuracy reporting specifically because of holiday fireworks. White said it’s “very rare” for fireworks to trigger a false alert.
SoundThinking recorded 34,818 total gunshots so far this year. Nearly half (45%) of the gunfire came from a portion of the 9th Precinct on Detroit’s east side near Harper Woods; the devices reported 15,497 gunshots as of July 24.
DPD reported 81 non-fatal shootings and 23 homicides in the 9th Precinct so far this year. Non-fatal shootings are down 16% compared to this point in 2022, while the department recorded one more homicide. Detroit does not report the number of fatal shootings in publicly available crime reports.
White and Mayor Mike Duggan told residents last year that SoundThinking would help prevent shootings. Since then, Moore said police commissioners have heard DPD shift focus to the technology’s impact on evidence collection.
Capt. Brandon Lewis of the 10th precinct told police commissioners this month the biggest benefit of SoundThinking is how it helps police recover shell casings and flesh out investigations. Lewis said police will often canvass scenes multiple times, sometimes with a metal detector, to find clues and interview potential witnesses.
Another major benefit, Lewis said, is how SoundThinking alerts help police locate shootings they otherwise wouldn’t know about. Lewis said residents “have become desensitized” to gunfire and don’t always report shots to 911. The police chief has consistently promoted how gunshot alerts have led to the recovery of evidence that results in arrests.
“A lot of our citizens are used to hearing gunshots, but you don’t want your community to be desensitized to gunfire,” White said in May.
“You’re going to see the benefit of having it,” White added. “It is a very powerful tool. It is not a biased tool. It only activates him and folks who are using a gun in our community. If you don’t want to engage (SoundThinking), don’t pull the trigger – it’s very precise.”
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