Robert Downey Jr. broke Halle Berry's arm during the hospital interrogation scene. Downey was supposed to grab Berry's arm and twist, but twisted too hard and her arm snapped. Production was halted for eight weeks.
Robert Downey Jr. and producer Susan Downey first met on the set and fell in love. They got married in August 27, 2005 and later started their production company Team Downey.
The scene in the pool was not scripted, but was added as a suspense sequence by director Mathieu Kassovitz.
Halle Berry was partly inspired to take the role of Miranda because her mother, a nurse, worked in a psychiatric hospital for decades. She prepared for the role by consulting her mother on how to convincingly play a psychiatrist.
The title of the film, Gothika (can also be spelled gothica), is an unofficial term used to describe a form of purgatorial state of mind, a situation in which someone sees or feels things that no one else does, and those who don't think those who can, are crazy. They simply have a connection to the supernatural world.