How does a thing become a person? In December 2013, the lawyer Steven Wise showed the world how, with a little legal jujitsu, an animal can transition from a thing without rights to a person with legal protections. This Op-Doc video follows Mr. Wise on his path to filing the first-ever lawsuits in the United States demanding limited “personhood” rights for certain animals, on behalf of four captive chimpanzees in New York State.

Mr. Wise (who is also the subject of The New York Times Magazine’s cover story this Sunday) has spent more than 30 years developing his strategy for attaining animal personhood rights. After he started his career as a criminal defense lawyer, he was inspired by Peter Singer’s book “Animal Liberation” to dedicate himself to justice for animals. He helped pioneer the study of animal rights law in the 1980s. In 2000, he became the first person to teach the subject at Harvard Law School, as a visiting lecturer. Mr. Wise began developing his animal personhood strategy after struggling with ineffective welfare laws and regulations that fail to keep animals out of abusive environments. Unlike welfare statutes, legal personhood would give some animals irrevocable protections that recognize their critical needs to live in the wild and to not be owned or abused.

The current focus of Mr. Wise’s legal campaign includes chimpanzees, elephants, whales and dolphins — animals whose unusually high level of intelligence has been recognized by scientific research. The body of scientific work on chimpanzee cognition, in particular, is enormous, and scientific testimony is crucial to Mr. Wise’s legal arguments. His team, the Nonhuman Rights Project (NhRP), selected as its first plaintiffs four chimps living in New York: Tommy, Kiko, Hercules and Leo. He chose these animals in large part because New York’s common laws are favorable to habeas corpus lawsuits, and because there are great ape sanctuaries that could accommodate them.

This fall, the cases will be likely to go to New York’s intermediate appellate courts. If Mr. Wise wins, he will have successfully broken down the legal wall that separates animals from humans. His plaintiffs, the four chimps, will be deemed legal persons and relocated to outdoor sanctuaries around the United States. In many ways, the lawsuits have already won: They have brought animal personhood to the forefront of the conversation surrounding our society’s relationship with animals.