An American lawyer and animal activist who is calling for primates to be recognised as people in the eyes of the law has had a breakthrough, with a New York judge agreeing to hear the case of two chimps he is representing.

The case has brought into question whether chimpanzees should be viewed as a person in the eyes of the law.

At the centre of the case are Leo and Hercules, two chimpanzees being used for biomedical experimentation at Stony Brook University in New York.

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Representing them are Steve Wise, the president of the Non-Human Rights Project, an initiative working to achieve equal rights for species other than humans.

He argues Leo and Hercules are being “unlawfully detained”.

“There are two chimpanzees, being Hercules and Leo, who are young male chimpanzees, they’re about eight years old. They’re being held in Stony Brook in New York on Long Island and it appears that they’re being used for some kind of history of locomotion or how locomotion occurred,” Mr Wise said.

He said the study the chimpanzees were being held for was to determine how humans came to walk upright.

“How chimpanzees were kind of bowlegged and how now we aren’t and those chimpanzees are being forced to live out their lives for what appears to be something that’s not worthwhile.”

Mr Wise said despite the chimpanzees technically being his legal clients he had not been allowed access to them and the university had not officially admitted to holding the animals.

“We have not been allowed to see them. In fact, the folks at Stony Brook have stonewalled us from top to bottom and they have never even admitted that they have them,” he said.

Justice Barbara Jaffe, from the New York State Supreme Court, is presiding over the case and has ordered, in the first instance, that the state provide an explanation as to why the two young chimps should not be released from captivity.

Mr Wise believes Justice Jaffe wants to dig even deeper into the case of Leo and Hercules.

“She doesn’t necessarily have to conclude that they are persons, but she clearly thinks that they might be and she wants to hear a full-scale argument on it,” he said.

Mr Wise said Justice Jaffe made an order in relation to the chimps which only applies to people, rather than things, which is how animals have previously been categorised.

“We brought in 100 pages of affidavits from experts around the world in chimpanzee cognition and they show that they are autonomous beings and they can self-determine,” he said.

“If we can win these cases, and we one day will, then the law will begin to go in all sorts of directions.”

Mr Wise envisages a new life for Leo and Hercules.

“They will be able to go to a place called Save the Chimps where they will be able to live with 25 other chimpanzees on an island and they will make up their own minds and live a chimpanzee life,” he said.