Yeah I think there's something to them taking that away whether they found anything they could use as evidence in it or not.
To my mind the idea Allison caused her own death by suicide or accident is even more of a stretch than that she was murdered. It'd have to go something like this...
She stays up to 1:30am or so even though she has to leave for a conference by 7. Even though it's late she very helpfully puts her husband's phone on the charger for him.
The next morning she wakes and dresses as her husband might expect to go for a walk, despite the likely earlier than normal departure and her freshly done hair.
She heads out for a walk and manages to trip over in the carport getting lots of plants all over her lovely new hair do. She's bleeding and rumbles around in the car for something, getting blood over the car. Despite the mess to herself she decides to continue with the walk anyway. Suddenly she becomes disorientated and goes into a psychosis and finds herself walking and walking for kilometres. She turns corner after corner and ends up on a busy state road with no side paths and traffic that is starting to build for peak hour but no one sees her even though she'd basically be on the road and still she walks and walks up hills and around corners all the while in this daze and then she finds herself at a bridge and she walks down and sits under the bridge. She doesn't throw herself off, she has no broken bones. She doesn't drown, the report says that too. She just quietly dies or in the stupor she manages to overdose on a tablet she hasn't fulfilled a prescription on for some time and that's hard to overdose on. That or she decided to walk for miles and miles on purpose to find somewhere hidden away to take it.
Meanwhile her husband wakes and sends her a text. She doesn't respond and by about 20-30 mins after that he's panicked, cut himself shaving worse than anyone in the history of man ever without noticing because he's so rushed and panicked, and called the police. By the time the police come to see him he's very calm in his answers, the panic seems under control.
But yeah that's a more plausible theory than the prosecution's according to the defence.