From 2009 to 2013, an oversight board substantiated nine complaints by people who said New York City police officers restrained them with a chokehold, a banned tactic that may have played a role in the death of a Staten Island man last week.

In each of the nine cases, the Civilian Complaint Review Board, an independent agency that investigates police misconduct, recommended that the Police Department pursue the strongest form of punishment for the officers: an administrative trial, which could lead to termination.

But the police commissioner has the final say in such cases, and in all but one of the cases decided, the officers were not disciplined, or were given the lightest possible sanction: a review of the rules.

The department’s response in the nine cases, documented in monthly reports by the board, raised uncomfortable questions for the Police Department, which prohibits chokeholds because of the risk of serious injury or death, but in practice appears to treat the maneuver as little more than a lapse.