US Supreme Court justices will not issue a decision until later this year — probably near the end of June — but today’s questioning suggested that they will find isolated human DNA ineligible for patents. The justices did seem inclined, however, to protect patents on cDNA, which is DNA synthesized using RNA as a template. (cDNA is often shorter and easier to manipulate in the lab than genomic DNA, and many patents on DNA sequences claim cDNAs.)

The case has been working its way through the courts since 2009, when the American Civil Liberties Union and the Public Patent Foundation filed a complaint against Myriad Genetics, a medical diagnostics company based in Salt Lake City, Utah, that holds patents on two genes related to breast and other cancers. The groups filed the complaint on behalf of patients, physicians and researchers who argued that the patents, which claimed isolated BRCA1 and BRCA2 genes, cover a product of nature and are therefore invalid.

In this morning’s arguments, the justices did not spend much time challenging the lawyer for the plaintiffs on that assertion, noted SCOTUS blog publisher Tom Goldstein, who hosted a panel discussion after the session. Instead, many of their questions focused on whether invalidating the patents would squelch the biotechnology industry, or if companies would have other avenues — such as patents on methods or cDNAs — available to protect their investment in research. That, said Goldstein, suggested the justices were testing the scope of their ruling, rather than whether the plaintiff’s argument was right or wrong: “I would be very surprised if the Supreme Court says isolated gene sequences would be patent-eligible subject matter after today’s argument.”