Oh, that's what I missed.
Mary, we're talking about suspicious behavior. Not behavior that was used to convict the duo, just behavior that lead to their further interrogations by Police Officers.
Not only is it very common for the people found at the scene of the crime, you know - the ones who discovered the scene - to be most heavily questioned. It is likewise suspicious for a pair with nothing to hide to do what they can to not be questioned alone.
Interestingly, as soon as the duo was questioned separately, Raffaele's alibi for him and Amanda broke down. You can imply/accuse the Police were responsible for implanting these "false memories" or "confessions" or that these two were under duress. But you have yet to actually prove that.
Of course the questioning got tough as the night wore on - the further into the interrogations the Police went, the more discrepancies were noted, and thus the story unraveled.
It takes far more than 1:45 for memories to be implanted. And it surely takes less than 2 weeks for the duress from an intense interrogation to wear off.
Of course, I suppose Amanda was still under duress due to being imprisoned.