This article (I took out the link you had because the article is behind a pay wall and you can’t access the full thing unless you find it through a search engine) is about an animal rights’ lawyer’s attempt to get chimpanzees to be labeled as “persons” by an American court. The lawyer feels that this will be a good way to start to gain animals some of the rights that he feels they deserve.
While the idea of calling animals “persons” may seem very odd, the article points out that there are precedents that would help to justify this. The author says that, particularly in medieval Europe, there was a tradition of putting animals on trial. He says that animals were, for example, hung for killing people unless they were exonerated at a trial. The author also points out that we Americans have legal traditions that call at least two non-human things “persons.” Legally, corporations are persons and have things like the right to free speech. Interestingly, ships are deemed to be “persons” as well, though they do not appear to have much in the way of rights.
The article offers a few other bits of hope for the lawyer bringing the case. For example, it says that the government of India declared dolphins to be “nonhuman persons.” It also says that the US Fish and Wildlife Service recommended that even captive chimps be put on the endangered list and protected that way. There are states where animals can own property left to them in wills, and the dogs of NFL quarterback Michael Vick were appointed a guardian ad litem (just as human children are) when he was convicted of animal abuse.
So, there are examples in history of putting animals on trial. This contrasts with our own modern system in which animals are typically treated as property without any rights.