Does anyone know how they found out that they had made Arthur stand in the hall and how they got the video of him in the house?
Ironically, and you'll love this. ET installed the living room CCTV supposedly on the advice of her hairdresser friend to have evidence that he was not being abused by her.
From that CCTV footage, and the fact that Arthur was forced to sleep on the floor of the living room in view of the CCTV, the police were able to establish how long Arthur was stood out in the hall based on his absence from the living room during his waking hours.
When the police initially arrived at the scene, she tried to knock the camera behind the TV so they wouldn't spot it.