Exercising a little-known authority called “retention,” the commissioner, Edward Caban, ensured the case would never go to trial.

Instead, Caban reached his own conclusion in private.

He decided that it “would be detrimental to the Police Department’s disciplinary process” to pursue administrative charges against the officer, Gerard Dowling, according to a letter the department sent to the oversight agency. The force that the officer used against Villafane was “reasonable and necessary.” The commissioner ordered no discipline.

Today, Dowling is a deputy chief of the unit that handles protests throughout the city.