Gothika (movie, 2003)

After a car crash, a criminal psychologist (Halle Berry) comes to, only to find that she's a patient in the same mental institution that currently employs her. It seems she's been accused of murdering her husband -- but she has no memory of committing the crime. As she tries to regain her memory and convince her co-workers of her innocence, a vengeful spirit uses her as an earthly pawn, which further convinces everyone of her guilt.