The Hercules the chimpanzee case was a 2015 New York lawsuit that asked a court to recognize two research chimpanzees, Hercules and Leo, as legal persons entitled to bodily liberty under a writ of habeas corpus. Justice Barbara Jaffe of Manhattan Supreme Court denied the petition, holding that she was bound by an earlier appellate ruling that animals cannot be “persons” for habeas purposes. She also wrote that the effort to extend legal rights to chimpanzees was “understandable” and “may even succeed” someday. The chimpanzees themselves were eventually retired to a sanctuary in Georgia.
Who Hercules and Leo Were
Hercules and Leo were born at the New Iberia Research Center in Louisiana. In 2009, when each was about a year old, they were leased to Stony Brook University’s Department of Anatomical Sciences on Long Island. For six years, researchers used them in locomotion studies aimed at understanding how humans evolved to walk upright. The work involved repeated general anesthesia and the insertion of fine-wire electrodes into their muscles.1Nonhuman Rights Project. Hercules and Leo
The Nonhuman Rights Project (NhRP), the advocacy group that brought the case, did not allege mistreatment or challenge lab conditions. Its argument was more fundamental. Holding these two chimpanzees at all, the group said, was itself a form of unlawful imprisonment.
Why the Case Used Habeas Corpus
A writ of habeas corpus is a court order that forces whoever is holding someone in custody to justify that detention. It is one of the oldest protections in Anglo-American law.2United States Courts. Habeas Corpus The NhRP chose the tool deliberately. If a court issued the writ for Hercules and Leo, it would implicitly treat them as persons rather than property, because only persons can be unlawfully detained.
The NhRP first filed in Suffolk County in December 2013 and was turned away. After refiling in Manhattan, the group got a further hearing: Justice Jaffe signed an order to show cause directing Stony Brook to appear and justify its detention of Hercules and Leo.3New York State Courts. Matter of Nonhuman Rights Project, Inc. v Stanley On May 27, 2015, Hercules and Leo became the first nonhuman animals in the world to be the subject of a habeas corpus hearing.
The Arguments on Each Side
The NhRP built its case on scientific evidence about chimpanzee cognition. Its attorneys filed expert affidavits documenting chimpanzee autonomy, self-awareness, and complex emotional and social lives. Beings with that level of cognitive sophistication, the group argued, are not “things.” They experience their confinement. That capacity for suffering and self-determination, in the NhRP’s view, was enough to qualify Hercules and Leo as legal persons entitled to bodily liberty.
The State of New York argued the opposite. Legal personhood, the state said, requires the ability to bear responsibilities. Rights come paired with duties: a person can be sued, held to a contract, and punished for breaking the law. Because chimpanzees cannot participate in the legal system in those ways, they cannot be considered legal persons. The state also warned that granting the writ would upend the treatment of animals as property and open the door to a flood of litigation.
What Justice Jaffe Decided
On July 29, 2015, Justice Jaffe denied the petition and dismissed the case. Her reasoning was candid. She thought the underlying question was unsettled, but she was bound by higher-court precedent. The Third Department of the Appellate Division had already ruled in a separate chimpanzee case that animals are “incapable of bearing any legal responsibilities and societal duties,” which made them ineligible for habeas corpus relief. As a trial judge, Jaffe could not overrule that.3New York State Courts. Matter of Nonhuman Rights Project, Inc. v Stanley
What made the opinion notable was everything Jaffe wrote around the holding. She said “the similarities between chimpanzees and humans inspire the empathy felt for a beloved pet” and called efforts to extend legal rights to chimpanzees “understandable.” She quoted Justice Kennedy’s observation in a different context that “times can blind us to certain truths and later generations can see that laws once thought necessary and proper in fact serve only to oppress.” She added that even if she were free of the precedent, the question was one best resolved by the legislature or the Court of Appeals, not a trial court.3New York State Courts. Matter of Nonhuman Rights Project, Inc. v Stanley
The ruling was a legal loss for Hercules and Leo. It was also the first time a New York judge had engaged seriously with the ethical case for animal personhood in a written opinion.
What Happened to Hercules and Leo
The court did not order their release, but the litigation generated enough public attention to change the outcome anyway. Stony Brook University ended its locomotion research and returned both chimpanzees to the New Iberia Research Center. From there, Hercules and Leo were retired to Project Chimps, a 236-acre sanctuary in the Blue Ridge Mountains near Morganton, Georgia. They arrived on March 21, 2018.4Project Chimps. Hercules
No judge ever recognized them as persons. No writ ever issued. But the institution holding them let them go, and for the two chimpanzees at the center of the case, that was the practical result the lawsuit had sought.
The Precedent That Bound Jaffe: Tommy and Kiko
The appellate ruling Justice Jaffe cited came from a separate NhRP case involving a chimpanzee named Tommy, kept in a cage in a shed on private property in Gloversville, New York. In 2014, the Third Department rejected the habeas petition, holding that animals “have never been considered persons for the purposes of habeas corpus relief” and reasoning that the “incapability to bear any legal responsibilities and societal duties” made it inappropriate to grant chimpanzees the fundamental right to liberty.5Justia. People ex rel. Nonhuman Rights Project, Inc. v Lavery
The NhRP brought a parallel case for a chimpanzee named Kiko. Both cases reached the New York Court of Appeals, which denied leave to appeal on May 8, 2018, without a full merits decision.6Justia. Matter of Nonhuman Rights Project, Inc. v Lavery
Judge Fahey’s Concurrence
The denial of leave produced what became the most widely discussed judicial writing in the animal personhood debate. Judge Eugene M. Fahey concurred in denying review but wrote separately to say the decision troubled him. He opened by calling the case a display of “the inadequacy of the law as a vehicle to address some of our most difficult ethical dilemmas.”7New York State Court of Appeals. In the Matter of Nonhuman Rights Project, Inc. v Lavery Fahey questioned the reliance on dictionary definitions of “person” and challenged the assumption that legal rights must be tied to the ability to bear legal duties. He wrote that “the issue whether a nonhuman animal has a fundamental right to liberty protected by the writ of habeas corpus is profound and far-reaching.”6Justia. Matter of Nonhuman Rights Project, Inc. v Lavery
What the Case Meant for Later Animal Personhood Cases
The NhRP’s next major case involved Happy, an Asian elephant at the Bronx Zoo. In June 2022, the New York Court of Appeals issued its first full merits decision in an animal personhood case. By a 5-2 vote, the court affirmed dismissal. Chief Judge DiFiore wrote that habeas corpus “is intended to protect the liberty right of human beings to be free of unlawful confinement” and “has no applicability to Happy, a nonhuman animal who is not a ‘person’ subjected to illegal detention.” The majority called extending personhood through habeas corpus a “sweeping pronouncement” that would displace existing animal welfare frameworks.8Justia. Nonhuman Rights Project, Inc. v Breheny Two judges dissented.
In 2025, the Colorado Supreme Court rejected an NhRP habeas petition filed on behalf of elephants at the Cheyenne Mountain Zoo, noting that “no Colorado court, nor any other court in any other jurisdiction in the United States has ever recognized the legal ‘personhood’ of any nonhuman species.”9Justia. Nonhuman Rights Project, Inc. v Cheyenne Mountain Zoological Society
Every habeas petition the NhRP has filed has been denied, for reasons that trace back through Happy, through Tommy and Kiko, and to the ruling on Hercules and Leo. The legal wall has held. What has shifted is the willingness of courts to engage with the underlying question, and that shift began with Justice Jaffe’s opinion in the summer of 2015.