Should techniques for training horses be eligible for a patent? What about a system for choosing a jury or fail-proof method for speed dating?

Supreme Court justices raised the questions Monday as they struggled to decide what types of inventions should qualify for patent protection.

In a case that has put software and bioscience companies on edge, the justices debated whether processes or methods of doing business should be eligible for protection. The dispute has raised serious questions about whether software programs, medical procedures, financial transactions and other nontangible inventions should be able to obtain patents like those granted to physical devices. And it left the high court grappling with the line between abstract processes and concrete applications.

Monday's oral arguments made clear that the justices are skeptical that the business method at the center of the case before them — a process of hedging weather-related risk in energy prices — deserves a patent. Some saw a risk in using the current case to set broad precedent on what can and cannot be patented.

The court's newest justice, Sonia Sotomayor, asked the lawyer defending the hedging application how the high court can limit patent protection to "something that is reasonable?"

In 1997, inventors Bernard Bilski and Rand Warsaw applied for a patent on a process that can be used by residential and commercial customers to lock in fixed energy bills, even during an unusually cold winter. The Patent Office concluded the process was too abstract and denied the application.

The U.S. Circuit Court of Appeals for the Federal Circuit upheld the Patent Office decision last year and said a process is eligible for a patent only if it is "tied to a particular machine or apparatus" or if it "transforms a particular article into a different state or thing." The circuit court said Bilski's process did not meet that test.

The question before the Supreme Court on Monday was whether the "machine-or-transformation" test is the right standard.

Michael Jakes, the attorney representing Bilski and Warsaw, told the high court that the test is too "rigid and narrow" and would exclude too many useful innovations in today's information-based economy, including his clients' hedging technique.