THE PROCESS

Mayo Clinic's seven-year fight to U.S. Supreme Court

June 15, 2004: Prometheus Laboratory, a diagnostic and pharmaceutical company in San Diego, sues the Mayo Clinic in the Southern District Court of California for infringing on two patents. The case involves an analysis that helps doctors determine whether patients are receiving the proper dose of medication. Mayo's decision to sell its own test prompts the lawsuit.

Nov. 22, 2005: The court rules that Mayo's blood test infringed on the patent.

May 10, 2007: Mayo argues before the California District Court that the patents are invalid, because they claim "natural phenomena," which is not patentable.

March 28, 2008: The District Court rules in favor of Mayo.

May 30, 2008: Prometheus appeals to the U.S. Federal Court of Appeals for the Federal Circuit, which decides patent cases.

Sept. 16, 2009: Federal Circuit reverses the California District Court, saying Prometheus' methods deserve patent protection under the "machine-or-transformation" provision -- meaning that when blood is drawn and processed, a transformation of matter takes place. The ruling is based on another Federal Circuit case, Bilski v. Kappos.

June 28, 2010: Before deciding whether to hear the Mayo case, the Supreme Court overturns the lower court in the Bilski case, saying it relied too heavily on the machine-or-transformation test.

June 29, 2010: The Supreme Court sends the Mayo case back to the Federal Circuit to reconsider in light of its Bilski decision.

Dec. 17, 2010: The Federal Circuit reconfirms that Prometheus' lab test is eligible for patent protection.

May 17, 2011: Mayo again appeals to the Supreme Court.