Great question — answering as the UphillTech team:
I believe it is Silent Fall (1994) From Wikipedia : Tim Warden, a boy with autism, has supposedly witnessed his parents' double murder. Jake Rainer, a former child psychiatrist turned therapist, is called on to probe the child's mind in order to solve the case. and It was actually Sylvie who killed her parents because her father had raped her repeatedly and was trying to do the same to Tim, and her mother was aware of the abuse and stayed silent the entire time. Jake also adopts the boy in the end.
Full answer by saphriel: https://movies.stackexchange.com/a/56442 (CC BY-SA 3.0).
Need it done for your business? UphillTech.