That's for the jury to decide, and is a major basis for the defense.
This case is all about numerous people remembering things which might not have made a precise impression at the time. People can misremember when, from whom, and even whether they heard something, they can also lie.
The defense doesn't need to convince the jury that any particular scenario is true, they only need to convince them that there is some doubt about what was really said by and to various people, or when. Alternatively, Libby might have misremembered, when questioned by the grand jury.
If the jury finds any of these conclusions to be plausible, then they must acquit. It's hard to get a perjury conviction. Especially if it looks like the prosecution may manipulated the investigation to target a particular person.
We need another source besides the Al AP to really find out what went on in the court room today.