Lawsuit accuses Chicago authorities of misusing gunshot detection system in a murder case

A 65-year-old man named Michael Williams spent almost a year in jail over the shooting of a man inside his car before prosecutors asked a judge to dismiss his case due to insufficient evidence. Now, the MacArthur Justice Center has sued the city of Chicago for using ShotSpotter, which it calls an “unreliable” gunshot detection technology, as critical evidence in charging him with first-degree murder. The human rights advocate group out of Northwestern University accuses the city’s cops of relying on the technology and failing to pursue other leads in the investigation.

Williams was arrested in 2021 over the death of Safarian Herring, a young man from the neighborhood, who asked him for a ride in the middle of unrest over police brutality in May that year. According to an AP report from March, the key piece of evidence used for his arrest was a clip of noiseless security video showing a car driving through an intersection. That’s coupled with a loud bang picked up by ShotSpotter’s network of surveillance microphones. ShotSpotter uses a large network of audio sensors distributed through a specific area to pick up the sound of gunfire. The sensors work with each other to triangulate the shot’s location, so perpetrators can’t hide behind walls or other structures to mask their crime.

However, a study conducted by the MacArthur Justice Center in 2021 found that 89 percent of the alerts the system sends law enforcement turn up no evidence of any gun-related crime. “In less than two years, there were more than 40,000 dead-end ShotSpotter deployments,” the report said. The group also pointed out that ShotSpotter alerts “should only be used for initial investigative purposes.” San Francisco’s surveillance technology policy (PDF), for instance, states that its police department must only use ShotSpotter information to find shell casing evidence on the scene and to further analyze the incident.

The lawsuit accuses Chicago’s police department of failing to pursue other leads in investigating Williams, including reports that the victim was shot earlier at a bus stop. Authorities never established what’s supposed to be Williams’ motive, didn’t find a firearm or any kind of physical evidence that proves that Williams shot Herring, the group said.

On its website, ShotSpotter posted a response to “false claims” about its technology, calling reports about its inaccuracy “absolutely false.” The company claims its technology has a 97 percent accuracy rate, including a 0.5 percent false positive rate, and says those numbers were independently confirmed by Edgeworth Analytics, a data science firm in Washington, D.C. It also answers the part of the lawsuit that criticizes Chicago’s decision to place most of it sensors in predominantly Black and Latino neighborhoods, which could lead to potentially dangerous clashes with the police. ShotSpotter said it’s a false narrative that its coverage areas are biased and racially discriminatory and that it works with clients to determine coverage areas based on historical gunfire and homicide data .

As AP reports, the lawsuit is seeking class-action status for any Chicago resident who was stopped because of a ShotSpotter alert. The MacArthur Justice Center is also seeking damages from the city for the mental anguish and loss of income Williams had experienced throughout the whole ordeal, as well as for the legal fees he incurred. Further, the group is asking the court to ban the technology’s use in the city altogether.