Wrong Claim Construction Leads To Erroneous Infringement And Validity Findings

After concluding that the district court impermissibly narrowed the asserted patent claims, the U.S. Court of Appeals for the Federal Circuit overturned a jury verdict invalidating those claims and ordered a new trial to consider evidence of commercial success.  ArcelorMittal France et al. v. AK Steel Corp. et al., Case No. 11-1638 (Fed. Cir., Nov. 30, 2012) (Dyk, J.) (Wallach, J., dissenting-in-part). 

In January 2010, ArcelorMittal sued AK Steel in district court alleging that AK Steel's aluminum-coated steel sheet products infringed certain claims of ArcelorMittal's boron steel sheet patent.  The district court issued a claim construction order largely favoring AK Steel's position.  In relevant part, the district court construed the term "a hot-rolled steel sheet coated with an aluminum or aluminum alloy coating" to include only steel sheets that had been reduced to a final thickness by hot-rolling.  This construction excluded steel that was first hot-rolled and