Update, 21 April: Science has learned that the court order referred to in this story has been amended. The words “writ of habeas corpus” have been struck out, suggesting that the court has made no decision on whether Hercules and Leo—two research chimpanzees at Stony Brook University in New York—deserve to be treated as legal persons. The Nonhuman Rights Project has responded to the amendment, stating, “This case is one of a trio of cases that the Nonhuman Rights Project has brought in an attempt to free chimpanzees imprisoned within the State of New York through an ‘Article 70-Habeas Corpus’ proceeding. These cases are novel and this is the first time that an Order to Show Cause has issued. We are grateful for an opportunity to litigate the issue of the freedom of the chimpanzees, Hercules and Leo, at the ordered May hearing.” Stony Brook has also issued a statement about the case: “The University does not comment on the specifics of litigation, and awaits the court's full consideration on this matter.”

Update, 22 April: The court hearing has been moved back from 6 May to 27 May. At that time, the judge will hear legal arguments regarding whether Hercules and Leo should remain at Stony Brook.

In a decision that seems to recognize chimpanzees as legal persons for the first time, a New York judge today granted a pair of Stony Brook University lab animals the right to have their day in court. The ruling marks the first time in U.S. history that an animal has been covered by a writ of habeas corpus, which typically allows human prisoners to challenge their detention. The judicial action could force the university, which is believed to be holding the chimps, to release the primates, and could sway additional judges to do the same with other research animals.

“This is a big step forward to getting what we are ultimately seeking: the right to bodily liberty for chimpanzees and other cognitively complex animals,” says Natalie Prosin, the executive director of the animal rights organization, the Nonhuman Rights Project (NhRP), that filed the case. “We got our foot in the door. And no matter what happens, that door can never be completely shut again.”

Richard Cupp, a law professor at Pepperdine University in Malibu, California, and a noted opponent of personhood for animals, cautions against reading too much into the ruling, however. “The judge may merely want more information to make a decision on the legal personhood claim, and may have ordered a hearing simply as a vehicle for hearing out both parties in more depth,” he writes in an e-mail to Science. “It would be quite surprising if the judge intended to make a momentous substantive finding that chimpanzees are legal persons if the judge has not yet heard the other side’s arguments.”

The case began as a salvo of lawsuits filed by NhRP in December 2013. The group claimed that four New York chimpanzees—Hercules and Leo at Stony Brook, and two others on private property—were too cognitively and emotionally complex to be held in captivity and should be relocated to an established chimpanzee sanctuary. NhRP petitioned three lower court judges with a writ of habeas corpus, which is traditionally used to prevent people from being unlawfully imprisoned. By granting the writ, the judges would have implicitly acknowledged that chimpanzees were legal people, too—a first step in freeing them.

The judges quickly struck down each case, however, and NhRP has been appealing ever since. Today’s decision is the group’s first major victory. In her ruling, New York Supreme Court Justice Barbara Jaffe orders a representative of Stony Brook University to appear in court on 6 May to respond to NhRP’s petition that Hercules and Leo “are being unlawfully detained” and should be immediately moved to a chimp sanctuary in Florida. Both animals have been used to understand the evolution of human bipedalism. (Stony Brook did not immediately respond to a request for comment.)

Prosin says that even if NhRP loses the case, it will use the habeas corpus ruling to sway judges in other jurisdictions. “It strengthens our argument that these nonhuman animals are not property,” she says. The group plans to file another case—this one involving a captive elephant—by the end of the year and has set its sights on other animals, including research animals, across the country. “We have the scientific evidence to prove in a court of law that elephants, great apes, and whales and dolphins are autonomous beings and deserve the right to bodily liberty,” she says.

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