LOS ANGELES (CBS) — The ACLU has filed a lawsuit against the Los Angeles County District Attorney and the Sheriff’s Department  — claiming both agencies sit on evidence that could help criminal defendants get a fair shake.

The ACLU claims the Sheriff’s department had a secret program to hide evidence of deputy assaults on jail inmates. And that the DA’s office refused to disclose evidence that could potentially help people charged with crimes.

“We don’t know how many cases have been contaminated,” ACLU officials said to KNX 1070′s Jon Baird.

A sheriff’s spokesman initially called the lawsuit “meritless.”

Meantime, the ACLU has also filed ethics complaints against the DA, Steve Cooley.