New York joins cities questioning ShotSpotter costs, benefits

ShotSpotter, a system U.S. police departments use to detect gunfire, resulted in New York Police Department officers spending hundreds of hours in a single month investigating incidents the officers could not confirm were in fact shots fired, according to an audit the New York City comptroller released last week.

But ShotSpotter contends the audit is focusing on the wrong metrics.

The NYPD will have spent more than $54 million on the gunshot-detection service from the time the department started using it in 2014 until December, the end of its current contract with SoundThinking, the California company that owns the system.

The audit, led by New York City Comptroller Brad Lander, analyzed ShotSpotter’s accuracy over several months in 2022 and 2023. When the system was performing at its best, 20% of ShotSpotter’s alerts related to “confirmed shootings,” the audit found. But its performance was often below that level: Of the 940 alerts officers responded to in June 2023, for instance, only 13% corresponded to confirmed shootings.

That’s not the measure of accuracy the contract uses, however. The contractual standard the NYPD set was that ShotSpotter would detect and identify the location of 90% of outdoor gunfire incidents in the coverage areas, with some exceptions based on weapon caliber and suppression. (Suppressors, also known as silencers, muffle the sound of gunfire.) ShotSpotter reached its 90% target “in almost all boroughs except Manhattan, but when measured against the number of confirmed shootings, performance is far lower,” the audit states.

“It was surprising to me to learn how ShotSpotter wastes thousands of hours of NYPD officers’ time every year, and it doesn’t necessarily make New York safer for cops to, say, chase after a car backfiring,” Lander said in an interview.

In its four-page response, the NYPD said it “is limited in what it can consider a ‘confirmed shooting’ in conjunction with a ShotSpotter alert by the nature of police work and alerts which don’t result in the recovery of evidence (i.e. ballistics, property damage, shell casings/live ammunition, firearms, video, ear or eyewitnesses and/or victims).”

The audit criticizes NYPD for not collecting data the comptroller and the public could use to evaluate the tool’s effectiveness and economy. Without that evaluation, the audit “therefore does not currently support renewal of the contract,” it states.

If NYPD renews the contract, Lander said, he would like to see a clause with consequences for the system providing too many false positives, including a structure to reduce the fee the city pays to SoundThinking if, say, more than half of all alerts sent to officers do not relate to a confirmed shooting.

How ShotSpotter works

In more than 160 cities, ShotSpotter has placed sensors in areas that are known to have high crime rates. The devices listen for sharp, loud sounds and transmit data to company employees who determine whether they sound like gunshots. If so, they notify the police. Due to how the sensors triangulate in a given area, the system can provide an exact location to police in about a minute.

What is often misunderstood is the human element at play here, says Tom Chittum, senior vice president of forensic services at ShotSpotter. “Our staff don’t just use their ears, but they have other elements to help them determine if a sound is a gunshot,” he notes. For example, they can listen for audio cues such as whistling associated with fireworks or look at the waveform of the audio data to determine whether that sound has a sharp rise and fall, or its distance from the nearest sensor.

In the NYPD audit report, the comptroller “is being disingenuous about what he found,” Chittum said. When NYPD records an unconfirmed shooting, “our system could have detected a real shooting, but the perpetrators may have fled, they may have collected casings, and witnesses don’t often stick around after calling 911.”

To read the complete article, visit Smart Cities Dive.