The deaths of unarmed civilians like Eric Garner in New York City and Michael Brown in Ferguson, Mo., led to demands for greater transparency in the workings of police forces all over the country. The need for more openness is especially pressing in New York, where a uniquely strict disclosure law has shielded from public view the records of individual officers, even those who have committed crimes.

In many states, including New York, it can be difficult for the public to even learn the names of officers involved in fatal shootings.

This is nothing new to criminal defense lawyers, who have been stymied in their efforts to obtain information about the police officers who take the stand to testify against their clients.