Articles from VFXWorld and CGSociety about the CGI. No, there are no dragons, spaceships or explosions in this film. But there is the City of Los Angeles in 1928. They could have shot this without effects, but they would have done so on the same boring city backlot that gets trotted out all the time, and they couldn't have done those wide establishing shots. Nice to see the cars changing between 1928 and 1935, also.
Apparently JMS is writing a book about the case.
Some quite surprising bit got left out. Northcott was mainly abusing the children and murdering them only incidentally. He was aided by the woman he believed to be his mother, who was actually his grandmother (yay for incest). She got a jail term.