Tommy, a 26-year-old former circus performer, lives on a caravan park in Gloversville in upstate New York, where he spends his days alone, confined to a shed and watching cartoons and nature programmes on television.
His lawyer, Steven Wise, says this is no kind of life for a human. But Tommy is a chimpanzee.
This week, in what is believed to be the first court case of its kind, Wise is arguing that Tommy and other chimps are entitled to "legal personhood".
The Boston lawyer, who is also the president of animal advocacy group the Nonhuman Rights Project, hopes a New York appeals court will rule that Tommy has been unlawfully imprisoned, and should be released to live with other chimps at a sanctuary in Florida.
Keeping Tommy alone in a cage is the same as keeping a human in solitary confinement, says Wise, who has spent much of his career trying to extend human rights and protections to other intelligent animals.