Chicago's Inspector General released a critical report Tuesday on the Chicago Police Department's use of gunshot detection system ShotSpotter as the city grapples with a surge in shootings this year. 

Shootings in Chicago are up 10% in 2021 over 2020 and up 65% over the same time frame in 2019, according to CPD data. 

The city signed a three-year contract in August 2018 with ShotSpotter, which uses a "patented system of sensors, algorithms and artificial intelligence" to detect gunshots, according to the company's website. Chicago police requested an extension of that contract last November and the city granted it the next month. 

The OIG report found that only 9.1% of ShotSpotter alerts that led to a police dispatch, 4,556 out of 41,830, produced evidence of a gun-related criminal offense. 

"From quantitative analysis of ShotSpotter data and other records, OIG concludes that CPD responses to ShotSpotter alerts rarely produce evidence of a gun-related crime, rarely give rise to investigatory stops, and even less frequently lead to the recovery of gun crime-related evidence during an investigatory stop," the report said. 

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The gunshots detection system came under increased scrutiny in April when a police officer shot and killed 13-year-old Adam Toledo following a ShotSpotter alert. Toledo was holding a gun that had been fired by another man minutes earlier, according to police. 

"OIG identified evidence that the introduction of ShotSpotter technology in Chicago has changed the way some CPD members perceive and interact with individuals present in areas where ShotSpotter alerts are frequent," Tuesday's report said. 

Police investigate a crime scene where three people were shot at the Wentworth Gardens housing complex in the Bridgeport neighborhood on June 23, 2021 in Chicago, Illinois. (Scott Olson/Getty Images)

Police investigate a crime scene where three people were shot at the Wentworth Gardens housing complex in the Bridgeport neighborhood on June 23, 2021 in Chicago, Illinois. (Scott Olson/Getty Images)

ShotSpotter has contracts with more than 120 cities, which the company says benefit from faster response times, more accurate locations and quicker victim transport times. 

A Chicago police spokesperson said Tuesday that the department's use of ShotSpotter has "detected hundreds of shootings that would have otherwise gone unreported."

"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 spokesperson told Fox News. "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."

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The OIG report cited a study by the Macarthur Justice Center earlier this year that found 89% of deployments after a ShotSpotter alert in Chicago turned up no evidence of a gun-related crime. ShotSpotter took aim at that study, saying that data from the Office of Emergency Management and Communications is "not designed to capture and account for any subsequent police action resulting from an initial ShotSpotter alert."

"The OIG report does not negatively reflect on ShotSpotter’s accuracy which has been independently audited at 97% based on feedback from more than 120 customers," a ShotSpotter spokesperson told Fox News. "Nor does the OIG propose that ShotSpotter alerts are not indicative of actual gunfire whether or not physical evidence is recovered."

The Associated Press contributed to this report.