So I guess I'm going to put together my George culprit theory now. I'm not going to spend my time on the how for the murders because getting around the red and explaining things away is pretty easy (and something Battler says in game 5 
gives me an excuse to not worry about it) So I'm going to focus on hints that make him capable of being the culprit as a narrative and a person instead. So rather than a theory to get around the red think of this as a character analysis.
The first part is George's interest in the occult/magic.
The second is George is the only person explicitly shown to be capable of Familicide.
Third he has tons of motive.
So these are my 31 pieces of evidence suggesting the George is the culprit
NEW EVIDENCE APPEARS.
According to a reliable, source, GEORGE STEALS CANDY FROM KIDS!