In Markman II the Supreme Court decided that Claim Construction is a legal issue to be decided by the Judge.
The process can be done in the beginning, end or any time during the trial.
The Judge phrases the Intrinsic evidence to make it easier for the jury to understand/vote.
If Extrinsic evidence (expert witnesses) are needed for Claim Construction, the testimony usually conflicts. If the Judge believes that testimony will help the Jury decide infringement issue, he allows them to hear it & sometimes even let's them cast a ballot (vrng case), allowing them to act in a advisory role. Deciding after listening to the experts is a Fact.
TEVA is fairly simple. Appellate can review Intrinsic evidence from scratch. Unless a "Clear Error" was made by the District Judge, CAFC cannot review the Extrinsic evidence (facts)