you are a sanctimonius and very rude person - I could say worse but I would be dragging myself down to your level. How come Ferguson is allowed to mess up and correct himself ? How come the police are allowed to mess up and correct themselves , how come the family are allowed to get confused mess up and correct themselves , how come Julie is allowed to "misunderstand" a man threatening to kill all his family - I see a distinct pattern here - you excusing professionals and family who had a mans freedom in their hands but still continued to mess up and change statements etc etc . And you can sit there and excuse them because it suits your arguments . Don't answer my post because I cant be bothered to read your posts until you fall off your high horse 
When someone makes a mistake it is apparent. Ferguson had time to prepare his statement in September and that is when he was the most accurate. He clearly made a mistake in saying the medication was fortnightly since he changed it to every month. We know that is correct because she was in fact given it each month by her doctor not every 2 weeks.
What she was prescribed is not all that significant what matters is what she was actually taking. She was prescribed medicaiton she wasn't taking and that actually played a role in how the Haldol was affecting her. The medication meant to counter the sedative effect as well as various side effects was not being taken. We know because it wasn't in her system. So that confirms the suspicions her doctor had that she was not taking it.
You seem to be taking issue that this is chalked up to mistakes as opposed to some intentional lie on the part of Ferguson. Why would he lie? What would be the endgame?
In contrast Jeremy did have something to gain from the lies he told. Jeremy had a reason to say he used the gun the week before the murders after denying it the day before. It is not a coincidence that he changed his tune after Police said Anthony was the last known user and said the gun had the moderator and scope attached when he found it and put it away. How would he forget using it multiple times the week before the murder and yet suddenly remember it after being told about the last known user?
He kept changing whether he called Julie befor eor afte rpolice. Clearly it was before police which is what he ended up admitting later though he kept trying to pretend he did it after. By the time he got off the phone with police it was well after even the most late account of when the call could have been made to her which is 3:30AM. Yet he was on the phone with police till 3:35-3:36. Why would he lie about phoning her after? Because it looks extremely suspicious to call her before police.
One has to look at all available evidence to assess whether a genuine mistake is made by someone or they are lying.