A car with dark tinted windows circles the block a few times before swerving onto the sidewalk. A handful of armed plainclothes police officers jump out and order everyone out of a double-parked car so they can search it, striking terror in the seconds before red and blue lights flash or an officer yells "police."

A similar scene plays out in dozens of cities across the country every day.

The beating and death of Tyre Nichols by five former Memphis police officers who were members of an anti-crime task force has renewed scrutiny on such squads, which frequently wear street clothes and often ar...