I don’t know where you’re getting this notion that speculation is evasion
The liar faces a conundrum. He can ask to modify the theory again, which is perfectly fine, but whatever he comes up with to accommodate “dog isn’t sick” fact will directly contradict the preceding “Gillian stole cookies but didn’t eat them” theory.
You’ve described this kind of speculation as specific to liars, yet innocent people will end up having to do it too.
If a client is either factually innocent or guilty-but-sober-minded, there’s no difficulty getting them to admit the incriminating nature of incriminating evidence.
If an innocent person was shown evidence, of course he’s going to try to explain why the evidence is consistent with his innocence. Why do you think he wouldn’t do this?
Food gets used up quickly, but it takes a long while to use up housing, so banning new housing really isn’t comparable to banning making food.