Wouldn't she then find it weird that he went out to buy more cleaning products with her despite the house still looking like a tip?
Your other examples of deception don't really compare to what SH is claiming to have happened, the majority are things the partner would do while the other partner wasn't present. With SH we're being asked to believe that she was completely oblivious to everything he did, from the kidnap kit in the boot, the violent struggle upstairs, putting the bag containing becky into the boot, the car being parked in a different way, his excuse that he parked that way to wash the car even though we know now it was raining at that time, him getting up in the night from their bed to go outside and carry in a body in a bag, she doesn't notice a big body shaped bag before it goes in the bathroom, doesn't think its odd that she's not allowed in the bathroom for days, doesnt notice the packages/suitcases containing body parts in the rest of the house when he says he moved them out of the bathroom, doesn't notice them being picked up in a van, even though she was supposedly there at the time. And today we hear that her DNA on the twsit of the bag containing some of Beckys body is a billion times more likely to have come from her having direct contact with the bag than any other way. I just don't buy that she's that oblivious or that he wouldn't have told her about his "brilliant" idea to teach Becky a lesson. They sound like they were a couple with few friends, who were joined at the hip most of the time.
He's a hoarder! He WOULD buy more bags etc!
S - 'Ere Nathan, what you buyin more bin bags for?'
N - 'Cause these bags look stronger than them others love and I do have a lot a lot a lotta stuff to clear out'
S - 'Oh okay then' ...
How? Why would Shauna notice that he'd filled his old hoarded suitcases with a chopped up body? When your house is full of THAT much stuff, you don't notice things any more.
Also, the reason we're all here is that we are nosy, inquisitive, questioning, observant, half intelligent people ... not everyone thinks like we do! Just because YOU think YOU would notice all these little things and immediately realise your fella had bumped off his step sister, doesn't mean your average Joe/Jane would.
Shauna's dna on a bag knot isn't enough proof for me that she did anything - bags don't come clinically sterile wrapped.
If this bag was taken downstairs and put somewhere, she could've picked it up and moved it (if there's a knotted bin bag, I'd shove my fingers through the knot to pick it up) or maybe she pulled a bag from the roll for her own rubbish ...
My other ideas of deception DO happen while the 2 people are together!
It wasn't a "body shaped bag" was it!
It matters not one bit to me whether she ultimately is convicted or not, I'm not about to start having 'Free Shauna' T-shirts printed ... I'm just trying to assumed she's innocent UNTIL I hear the BOOM - there's your beyond reasonable doubt evidence.
ETA - Just because Nathan tells us he has Fibro doesn't mean he actually has fibro and even if at some point a Dr has said 'ooh I think you might have fibro' it doesn't necessarily mean that in the heat of the moment, when necessity calls, and adrenalin kicks in, that he couldn't do what needs to be done.