Past Sins (2006)

Donna Erickson, an overworked public defender, is in the middle of a tricky case — she's representing a woman suspected of committing a murder that happened years ago. Even though recent DNA evidence lays the blame on her client, this legal eagle has a gut feeling that her defendant is innocent. But the only way she can prove it is to go digging into the past of the accused. Your jaw will drop when you learn what she finds out!