Controversial gunshot detection technology used in cities nationwide is highly inaccurate and leads to disproportionate surveillance of minority communities with little payoff in terms of reducing crime, according to a report released Wednesday.

The report from the public defender organization Brooklyn Defender Services is based on a sample of 62,000 ShotSpotter gunshot alerts New York Police Department (NYPD) officers responded to over nine years. Their findings show the police could only confirm the alert correctly identified gunfire 16% of the time.

The police records — obtained by Brooklyn public defenders under a Freedom of Information Act request — indicate the department confirms the alerts in a number of ways, including through calls reporting gunfire, surveillance camera footage and property damage, shell casings, bullet fragments or an injured person found at the scene.

Alerts in New York City led to guns being recovered only .8% of the time and resulted in arrests for illegal activity just .7% of the time, according to the report, which is based on all ShotSpotter alert records in the city since 2015, when the system launched. 

The performance data sample underlying the report is the largest ever obtained from a police department using the technology.

ShotSpotter has long been criticized by privacy and civil liberties advocates for how its allegedly inaccurate reporting leads to overpolicing and surveillance of Black and Latino neighborhoods. The gunshot detectors are mainly used in minority communities.

The NYPD data reflected that criticism, showing that alerts led to police being deployed to predominantly Black neighborhoods 3.5 times as often as predominantly white ones.

A spokesperson for ShotSpotter did not immediately respond to a request for comment.

NYPD provided a statement saying that it “consistently reviews the effectiveness of technologies it utilizes to combat crime.” 

“ShotSpotter remains an integral tool in the NYPD’s mission of addressing gun violence and keeping the public safe,” they said.

Brooklyn Defenders disagreed, calling the gunshot detection system an “unreliable informant with police using its alerts to justify stops and frisks without legal justification.” 

“Essentially, ShotSpotter functions like an unreliable informant with police using its alerts to justify stops and frisks without legal justification,” the report says. 

“This pattern not only leads to unjustified stops, but also increases the chance that police responding to an alert will respond with hypervigilance, raising the risk of escalation during interactions that are based on faulty information.”

Chicago stopped using ShotSpotter, which relies on artificial intelligence algorithms and microphones to detect gunfire, in September. Several other major cities nationwide continue to deploy the system despite a number of studies showing it is often inaccurate and leads to overpolicing in poor and minority neighborhoods.

The NYPD has spent $45 million on the technology and hundreds of thousands more deploying personnel to neighborhoods in response to alerts, the report asserts, citing the fact that officers spend about nine hours in the neighborhoods SpotShotter sends them to after a notification.

ShotSpotter has long been criticized for alerting police to gunshots when it is in fact hearing fireworks or other loud noises that are not gunfire. The new report shows that alerts increased in New York City by more than 200% on July 4 and more than 175% on New Year's Eve.