Unfortunately this can lead to a catch-22, where you statistically know that people are being harmed, but without a lawsuit you can't identify specific people, and without specific people you can't launch a lawsuit. I feel that something like what happened with some of the government spying stuff in the last decade or so.
I can't find the story, but there have been a lot of people who wanted to sue as victims of PATRIOT ACT spying, but who couldn't because they couldn't actually prove they'd been spied upon. The lawyer for one such person was accidentally sent papers by the government (as part of a larger, intentional shipment of relevant papers) acknowledging such spying had occurred, but (I think) FBI agents showed up at his door the next day and demanded their return.
One could argue that, but then those clients, not the PD, should be bringing the suit.
One could even argue that the public defender's clients were affected, this impacting him.