Court realizes the worry that the doctrine of equivalents grants patents processes beyond their claims. This could be a problem. They say that it can only be applied to specific elements of a patent, not the patent as a whole.
This case: dye ultrapurification system using a membrane of pH between 9 and 6. They made this distinction based on the fact that an earlier patent was for the process using pH's above 9. They however give no reason for the 6 pH minimum. The alleged infringer used a pH value of 5. This is not disputed. The disputed is that 9-6 is substantially the same as 5. Judges in earlier court held the patent valid and infringed. ALl SC judges reversed their decisions and held that it was not infringing, it is the burden of the patentee to claim their patent, they claimed 9-6 and gave no reason for 6. Just because they can prove it works post-lawsuit for lower pH's doesnt make their patent valid for those pH's. Held patent uninfringed.