Law & Order: Special Victims Unit: Season 9, Episode 4

Savant

Ben Nicholson (Aidan Quinn) discovers that his mentally challenged daughter, Katie (played by Paulina Gerzon), who has Williams syndrome, is the only witness to the savage beating of his wife (Judy Kuhn), which placed her in a coma. Detectives Benson and Stabler and ADA Novak work with Katie to reconstruct the night the beating took place.