Sociopathy/lack of empathy is the main hindrance in life for people with ASD: not picking up the right signals, the nuances, having to learn the correct response/behaviour instead of it coming intuitively. People at the high functioning end blend in because they learn the most 'etiquette' but in unusual circumstances, where they have no prior pattern to follow, they tend to do things that seem slightly 'off' or completely unfathomable to neurotypical people. When they're aware they can't cope and don't know what to do, they adopt a familiar routine or do something that they think acts as a cover but doesn't. If my husband isn't coping socially he might suddenly decide to do the ironing, for example, or washing the kitchen windows - stuff he wouldn't normally do but it gives him an excuse not to talk to visitors who bore him (and so just looks rude

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JB's genetic father is an Army Officer, which statistically is another major red flag. (My husband was too ;-) )
His response to the deaths was to take on the admin of the farm - mid-harvest and people on weekly wages that was critical - ask the secretary to tidy the office paperwork, ask his cousin to be Farm Manager, organise money and legal documents - and abdicate responsibility for everything unusual/personal to his female relatives and friends (AE seemed more than happy to barge in and take over!). When someone dies there is a huge amount of admin: when my mother died my father, who has been the executor of umpteen other people's wills and organised lots of funerals, went completely to pieces - he left pretty much everything to me. We also ate out a lot because all the talking and decisions meant we weren't so good at doing the grocery shopping and it was just quicker,messier and frankly a relief to go to the village pub: I has never occurred to me other people would find that odd/lacking in empathy/disrespectful?
The fact JB has never be shown to have any mental health issues (which are different to ASD) makes him different, yet again, to most of the other prisoners on a whole-life tariff. A large component of the belief he committed the murders seems to rely on 'give a dog a bad name and hang him'. I really don't find his behaviour too odd, in this day and age when we are more accepting of differences.
I think one of his biggest mistakes was being influenced by Brett Collins, who sounds like a conman who took for a ride: I wonder how much that Meissen clock REALLY fetched . . . ? Was it him, staying in SC's flat, who found the topless modelling photos and took them to Fleet Street I wonder. JB doesn't seem to be a very good judge of character (other flag for ASD).