For the past three years, an attorney has been filing lawsuits in New York state on behalf of four chimpanzees. They are intelligent and self-aware, he argues. That’s why they should be treated as “persons” for legal purposes, and they should not be kept in cages. The lawsuits are based on habeas corpus, a legal doctrine that prevents an accuser from imprisoning someone without bringing charges against them in a court of law.  So far, courts in New York have denied the petitions and appeals ruling that animals may have rights but they cannot bear duties, and that excludes them from “personhood”. But legal experts say the definition of personhood is about “rights or duties,” not “rights and duties.” A legal battle with implications far beyond four chimpanzees in New York zoos.