Quite the reverse, it would seem. How does a "confused" person decide she was spending all night with her boyfriend [which puts her with the knife, bleach -remember her poor hygiene habits which led to frequent fights - and blood soaked sponge in her BF's home] and later when there is evidence found that she was in the home, she "remembers" that she was at home, which puts her with the body, the cleaned up evidence and the bloody footprints?
Very easily, if the interrogator is good at his job. As I said earlier, coax, threaten and reassure a vulnerable and ignorant suspect enough, and they will say whatever you want to hear if they think it will get them off the hook. Indeed, in the scenario I mentioned earlier, I started off stating that I could not remember where I was on that day. After being interrogated (ie. badgered) for an hour, I 'remembered' precisely what the principal wanted, because he stated in a reassuring voice that simply being in the vicinity and witnessing what might have been the infraction was not against school policy, and that to continue denying that I was there would lead to a suspension.
I'd love to see the transcript of the interview with Knox.