Now, let's be realistic.
How many "I'm sorry, but I don't recall," or "I have tried to remember that happening, but I'm just drawing a blank," or "I have no memory of anything like that -- I'm being totally honest with you," or similar, do you think we will hear? It may be an honest answer from one of them, but if we hear it from all of them, it will jog the hinky meter a bit, doncha think? I'd bet money on it.
Maybe if the FBI agent hooked them up to their version of a hinky meter, it might turn out differently.
I also wonder if the FBI will be allowed to use a lie-detector.
JMHO.
So far, IIANM, CF is the only one in this thing to have taken a lie detector test, which, in her case showed no evidence of lying.