The case focuses on a patent that covers the concept of adjusting the dosage of a drug, thiopurine, based on the concentration of a particular chemical (called a metabolite) in the patient's blood. The patent does not cover the drug itself—that patent expired years ago—nor does it cover any specific machine or procedure for measuring the metabolite level. Rather, it covers the idea that particular levels of the chemical "indicate a need" to raise or lower the drug dosage.
The patent holder, Prometheus Labs, offers a thiopurine testing product. It sued the Mayo Clinic when the latter announced it would offer its own, competing thiopurine test. But Prometheus claims much more than its specific testing process. It claims a physician administering thiopurine to a patient can infringe its patent merely by being aware of the scientific correlation disclosed in the patent—even if the doctor doesn't act on the patent's recommendations.
This extraordinary claim prompted a broad coalition of public interest groups to write amicus briefs urging the Supreme Court to invalidate the patent and others like it. The American Association of Retired Persons and the American Civil Liberties Union both wrote briefs arguing the patent should be invalidated. The ACLU brief argued that regulating doctors' thoughts runs afoul of the First Amendment.
Justices Scalia and Breyer showed some skepticism that patents could cover the use of scientific correlations in medical practice. But the other justices expressed no such skepticism. At one point, Justice Kagan offered some advice to Prometheus's lawyer. "What you haven't done is say at a certain number you should use a certain treatment, at another number you should use another treatment," she said. "I guess the first question is why didn't you file a patent like that? Because that clearly would have been patentable. Everybody agrees with that."
These are the same people that let companies patent the "Buy it Now" button, refuse to address patent trolling, and caused the multi-billion-dollar portfolio war between electronics companies. This money isn't spurring innovation, it's quashing it.
If you haven't been following the patent fiasco, I highly, highly recommend the three-part This American Life series "When Patents Attack!" It's available for free online streaming or from the iTunes store.