Christine's phone was found downstairs in the kitchen drawer and photographed by the police.
Christine's phone was used to unlock the front door for Joseph.
It doesn't make sense that Christine would leave her phone downstairs after unlocking the door. It makes sense that Brendan did it in preparation for the murders so Christine could not call for help.
This detail was overlooked by Brendan, IMO. I wonder if the phone was supposed to be retrieved by Brendan or Juliana and brought back upstairs to the bedroom.
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