WASHINGTON — In a lively Supreme Court argument on Monday, the justices struggled to find a narrow way to rule on the momentous question of whether human genes may be patented.
“Why should we jump in and decide the broadest possible question?” asked Justice Samuel A. Alito Jr.
To simplify the complex scientific and legal questions before them, the justices kicked around analogies — to chocolate-chip cookies, baseball bats and plants in the Amazon with medicinal qualities. But none of them proved wholly satisfactory, and Justice Stephen G. Breyer said there was a lesson in that.
“The patent law is filled with uneasy compromises,” he said. Some justices expressed concern about making sure that businesses continue to engage in expensive research. Others worried that allowing genes to be patented would shut down innovation.
“Why would a company incur massive investment if it cannot patent?” asked Justice Antonin Scalia.
But Justice Sonia Sotomayor suggested that an isolated gene was “just nature sitting there.”
The court’s ruling will shape the course of scientific research and medical testing, and it may alter the willingness of businesses to invest in the expensive work of isolating and understanding genetic material. The decision may affect not only thousands of patented genes but also pharmaceuticals, vaccines and genetically modified crops.
The case concerns patents held by Myriad Genetics, a Utah company, on genes that correlate with increased risk of hereditary breast and ovarian cancer. The central question for the justices in the case, Association for Molecular Pathology v. Myriad Genetics, No. 12-398, was whether isolated genes are “products of nature” that may not be patented or “human-made inventions” eligible for patent protection.
The patents were challenged by scientists and doctors who said their research and ability to help patients had been frustrated. Lower courts ruled that all but one of them, Dr. Harry Ostrer, lacked a stake in the case direct enough to give them standing to sue.
Christopher A. Hansen, a lawyer for Dr. Ostrer with the American Civil Liberties Union, said Myriad deserved credit for its work, but not a patent.
“What exactly did Myriad invent?” Mr. Hansen asked. “The answer is nothing.”
A lawyer for the company, Gregory A. Castanias, said the genes do not occur in nature and were isolated thanks to human ingenuity. “There was invention in the decision of where to begin the gene and where to end the gene,” he said.
Last year, a divided three-judge panel of a federal appeals court in Washington ruled for Myriad. Each judge issued an opinion, and a central dispute was whether isolated genes are sufficiently different from ones in the body to allow them to be patented.
The ruling followed a unanimous Supreme Court decision last year that said medical tests relying on correlations between drug dosages and treatment are not eligible for patent protection. Natural laws, Justice Breyer wrote for the court, may not be patented standing alone or in connection with processes that involve “well-understood, routine, conventional activity.”
Solicitor General Donald B. Verrilli Jr., representing the federal government, largely supported Dr. Ostrer and said last year’s decision, Mayo Collaborative Services v. Prometheus Laboratories, suggested that the correct answer in the case argued Monday was that merely isolating a gene was not sufficient for patent protection. But manipulating a gene to create something not found in nature would be, he added.
That distinction, coupled with possible patents for particular uses of genes, seemed attractive to several justices, particularly after Justice Elena Kagan asked a series of questions testing the scope of Mr. Castanias’s argument.
“Do you think that the first person who isolated chromosomes could have gotten a patent on that?” she asked.
Mr. Castanias said that was possible.
Justice Kagan said that was a significant concession.
“We could just go up from there and talk about all kinds of parts of the human body, couldn’t we?” she asked. “Couldn’t we get to, you know, the first person who found a liver?”
Other justices tried to reason by analogy.
Justice Sotomayor said an isolated gene was like an ingredient in a kitchen pantry.
“I can bake a chocolate-chip cookie using natural ingredients — salt, flour, eggs, butter,” she said. “And if I combust those in some new way, I can get a patent on that. But I can’t imagine getting a patent simply on the basic items of salt, flour and eggs.”
Mr. Castanias proposed a different analogy.
“A baseball bat doesn’t exist until it’s isolated from a tree,” he said. “But that’s still the product of human invention to decide where to begin the bat and where to end the bat.”
Chief Justice John G. Roberts Jr. did not appear convinced.
“You don’t look at a tree and say, well, I’ve cut the branch here and cut it here, and all of a sudden I’ve got a baseball bat,” he said. “You have to invent it, if you will.”
Justice Alito asked about “the leaves of a plant that grows in the Amazon, and it’s discovered that this has tremendous medicinal purposes.”
“Let’s say,” he said, that “it treats breast cancer.”
Mr. Hansen, the lawyer challenging the patent, said the mere discovery and extraction of the plant should not make it eligible for patent protection.