The de novo standard has always been used for CAFC patent appeals. It was recently reaffirmed in Lighting Ballast Control LLC v. Philips Elecs. North Am. Corp.

It will be interesting to see whether Grewal's analysis stands up.

Under do novo, no deference is given to the district court claim construction. Reversal happens in over 50% of cases. That being said, there aren't that many cases where you've got a technically savvy district court judge making the lower court decision.