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The company that sells the technology said the legislators’ claims are “a baseless attempt to disparage this critical public safety technology.”

Several Mass. legislators sent a letter to the Department of Homeland Security (DHS) Tuesday urging the office to investigate federal funding of a controversial audio gunshot detection technology, saying the system may violate civil rights. 

The letter, signed by Sen. Ed Markey, Sen. Elizabeth Warren, and Rep. Ayanna Pressley, says the technology, called ShotSpotter, contributes to over policing in Black and Latino communities and calls into question the technology’s accuracy. 

ShotSpotter is an acoustic gunshot detection system, sold by company SoundThinking, that aims to help police officers detect shots fired incidents quicker, especially when there isn’t a 911 call associated with the incident. The company contracts with municipalities who want to use the system, then installs sensors where shooting rates are the highest, it says. 

The technology is currently in use by multiple Massachusetts cities, including Boston, Cambridge, Worcester, and Chelsea, according to their respective police departments. 

Though SoundThinking claims ShotSpotters has an accuracy rate of 97%, Tuesday’s letter says that “reporting shows high error rates” and that there is an “over-deployment” of sensors in minority communities. Legislators point to data from Cambridge that showed the system had a false positive rate of 82% and numbers from Boston that suggest police found no evidence of gunfire in about 70% of ShotSpotter alerts.

“Studies have also shown that biased deployment of the system can perpetuate the over-policing and unjustified surveillance of communities of color, exposing residents to police interrogations, confrontation, and potentially creating dangerous situations for residents,” the letter, addressed to Inspector General Joseph V. Cuffari, reads. 

Legislators point to purportedly leaked data of ShotSpotter locations — which are unknown to even police departments that use the system — obtained by WIRED that shows sensors are concentrated in communities of color. In Boston, data showed that microphones are placed mainly in Dorchester and Roxbury. 

In response to the letter, SoundThinking said its team has not “drilled down into every claim in detail” but stood by the technology. 

“On the surface, we believe this letter and its claims are without merit and we are confident that the DHS will see through this baseless attempt to disparage this critical public safety technology,” a spokesperson for the company said in a statement to Boston.com. “ShotSpotter saves lives in the places hit hardest by gun violence.”

The letter specifically says the technology should be investigated as a violation of the Civil Rights Act of 1964, which prohibits recipients of federal financial aid from discriminating based on race, color, and nationality. 

The DHS provides funding to municipalities to deploy ShotSpotter through the Urban Area Security Initiative Grant program, according to the letter, which asks whether that money is “an appropriate use of taxpayer dollars.”