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CHICAGO — A report from the Chicago Office of Inspector General released Tuesday concluded that the Chicago Police Department’s use of ShotSpotter technology rarely leads to evidence of a gun-related crime and has changed the way some CPD members interact with people in communities where ShotSpotter alerts are frequent.

The city entered a three-year, $33 million contract with ShotSpotter in August 2018 and extended the contract in December 2020, well before the expiration of the previous contract. The city’s contract with ShotSpotter now runs until August 19, 2023.

The report said that data examined by the OIG does not support the conclusion that ShotSpotter helps lead to evidence of a gun-related crime. The report further states that if the result is attributed to missing or non-matched records of investigatory stops that did originate from a ShotSpotter alert, CPD’s record-keeping practices have obstructed a meaningful analysis of ShotSpotter’s effectiveness.

The OIG report analyzed CPD and OEMC data regarding all ShotSpotter alerts from January 1, 2020 to May 31, 2021, as well as analyzing investigatory stops confirmed to be linked to a ShotSpotter alert.

The report revealed the following:

  • A total of 50,176 ShotSpotter alerts were confirmed as ‘probable gunfire’, issued an event number, or a unique ID number assigned to distinct events of police activity and dispatched by OEMC. Each alert resulted in a CPD response to the location.
  • Of the 50,176 confirmed alerts, 41,830 report a disposition, or the outcome of a police response to the incident. Of these dispositions, a total of 4,556 incidents indicate evidence of a gun-related crime, accounting for 9.1 percent of CPD’s responses to ShotSpotter alerts.
  • Among the 50,176 confirmed and dispatched ShotSpotter alerts, a total of 1,056 share their event number with at least one investigatory stop report, indicating that a stop was a direct result of a ShotSpotter alert. That is, at least one investigatory stop is documented under a matching event number in 2.1 percent of all CPD responses to ShotSpotter alerts.
  • Through a separate keyword search analysis of all investigatory stop report narratives within the timeframe of the report, OIG identified an additional 1,366 investigatory stops potentially associated with ShotSpotter alerts whose event number did not match any of the 50,176 confirmed and dispatched ShotSpotter alerts.

OIG’s report further states that the presence of ShotSpotter technology is changing police behavior. Specifically, the OIG reviewed instances in which CPD officers rely, at least in part, on a perceived aggregate frequency of ShotSpotter alerts in a given area to from the basis of an investigatory stop or as part of the rationale for a pat-down once the stop is initiated.

Additionally, the OIG said that stronger data on law enforcement outcomes from ShotSpotter alerts would be valuable to assessing the usefulness of the technology and whether or not to continue the city’s partnership with ShotSpotter.

ShotSpotter uses a network of acoustic sensors to locate and identify suspected gunshots and is currently used in more than 100 American cities.

Deborah Witzburg, the Deputy Inspector General for Public Safety, offered this statement:

“Our study of ShotSpotter data is not about technological accuracy, it’s about operational value. If the Department is to continue to invest in technology which sends CPD officers into potentially dangerous situations with little information – and about which there are community concerns – it should be able to demonstrate the benefit of its use in combatting violent crime. The data we analyzed plainly doesn’t do that. Meanwhile, the very presence of this technology is changing the way CPD officers interact with members of Chicago’s communities. We hope that this analysis will equip stakeholders to make well-informed decisions about the ongoing use of ShotSpotter technology.”

Tom Ahern, Deputy Director of CPD News Affairs & Communications released the following statement after the OIG report’s release:

“In order to reduce gun violence, knowing where it occurs is crucial. ShotSpotter has detected hundreds of shootings that would have otherwise gone unreported. ShotSpotter is among a host of tools used by CPD to keep the public safe and ultimately save lives. Using ShotSpotter, CPD receives real-time alerts of detected gunfire enabling patrol officers to arrive at a precise location of a shooting event quickly. Instead of relying on the historically low rate of 911 calls, law enforcement can respond more quickly to locate and aid victims, identify witnesses and collect forensic evidence. The system gives police the opportunity to reassure communities that law enforcement is there to serve and protect them and helps to build bridges with residents who wish to remain anonymous.”

ShotSpotter offered an official statement in response to the OIG’s report:

“It is important to point out that the Chicago Police Department continually describes ShotSpotter as an important part of their operations. The OIG report does not negatively reflect on ShotSpotter’s accuracy which has been independently audited at 97 percent based on feedback from more than 120 customers. Nor does the OIG propose that ShotSpotter alerts are not indicative of actual gunfire whether or not physical evidence is recovered. We would defer to the Chicago Police Department to respond to the value the department gets from being able to precisely respond to criminal incidents of gunfire. We work very closely with our agency customers to ensure they get maximum value out of our service.”