This moggy covered (here and here) the UK litigation of Generics (t/a Mylan) v Yeda/Teva, in which a patent that covered glatiramer acetate (copolymer 1 or copaxone) was held valid despite having a few issues, one of which was that the claims specified a particular molecular weight range, but did not specify what method was used to measure the molecular weight. This finding was upheld on appeal as reported by Jeremy here.
Justice Breyer gave the Opinion of the Court with which Roberts, Scalia, Kennedy, Ginsburg, Sotomayor and Kagan joined; Justice Thomas filed a dissenting opinion in which Alito joined. According the majority opinion the Federal Circuit had indeed impermissibly conducted a de novo factual review. So the Federal Circuit's decision was vacated and the case remanded.
In the dissenting view, the opinion was that the Federal Circuit had not overturned findings of fact, but had instead formed a different conclusion of law as to the claim construction. Therefore, there had been no breach of the Federal Rules of Civil Procedure.
So back to the Federal Circuit before we find out what happens to the case substantively!