Violent crime in Mexico has pushed Mexican law enforcement to find new ways to fight crime, and one of the most innovative experiments is taking place in Oaxaca: According to local news reports, a team of 20 deaf police officers monitoring 230 security cameras scattered throughout the city’s historic downtown.

The deaf officers, nicknamed the “Angels of Silence,” are considered an asset because of their ability to read lips, to detect visual cues that might suggest nervousness or suspicious activity, and to pay attention to the visual periphery as they stare at a wall of monitors displaying different camera feeds.