Steven M. Smart, a pioneering animal rights lawyer who gave voice to purchasers unable to testify on their very own behalf, demanding the identical ethical and authorized entitlements as their house owners, keepers and custodians, died on Feb. 15 at his dwelling in Coral Springs, Fla. He was 73.

The trigger was problems of glioblastoma, an aggressive kind of mind most cancers, his baby Siena Smart mentioned.

Like John Scopes, the Tennessee trainer of evolution at the middle of the so-called monkey trial 9 many years earlier, Mr. Smart misplaced his authorized battles — attempting in his case, to not improve animals as our quick antecedents on the human household tree however to acknowledge their personhood as cognitive, emotional and social beings who’ve the identical ethical and statutory entitlement to freedom that folks do. (Not like Mr. Smart, John Scopes gained on enchantment.)

Mr. Smart was the primary president of the Animal Authorized Protection Fund and the founder and president of the Nonhuman Rights Project. He additionally taught programs on animal rights at Harvard and different legislation colleges.

He wrote a number of books, together with “Rattling the Cage: Toward Legal Rights for Animals” (2000), which the authorized scholar Cass R, Sunstein, in a New York Occasions evaluation, known as “an impassioned, fascinating and in many ways startling book”; “Drawing the Line: Science and the Case for Animal Rights” (2002); “Though the Heavens May Fall: The Landmark Trial That Led to the End of Human Slavery” (2005), a greatest vendor about an English case that decided {that a} slave was an individual with authorized rights; and “An American Trilogy: Death, Slavery, and Dominion on the Banks of the Cape Fear River” (2009).

In 2013, after many years of authorized and scientific analysis, the Nonhuman Rights Venture filed what it characterised as a groundbreaking writ of habeas corpus — requiring the authorities to provide an incarcerated individual earlier than a decide. Nevertheless, the petition was not for a human being however for Tommy, a chimpanzee being held in a shed at a used-trailer lot in Gloversville, N.Y., by a person who mentioned he had rescued him from someplace even worse.

Beforehand, legal professionals had expanded the definition of animal welfare (versus animal rights) by encompassing the remedy of animals in scientific analysis and in animal husbandry. Evaluating authorized attitudes towards animals with human enslavement earlier than the Civil Battle, Mr. Smart mentioned animal rights legal guidelines would provide extra safety than anti-cruelty statues in opposition to, for instance, state-sponsored deer hunts and the Navy’s deployment of dolphins on life-threatening duties.

“Certain species are capable of complex emotions, can communicate using language and have a sense of self,” Mr. Smart mentioned in a 2005 lecture, “all characteristics that once defined humanity.”

“I don’t see a difference,” he added, “between a chimpanzee and my 4-year-old son.”

After dropping in a decrease courtroom, Mr. Smart argued earlier than an Appellate Division panel in Albany, N.Y., that Tommy “can understand the past, he can anticipate the future, and he suffers as much in solitary confinement as a human being.”

Mr. Smart was not proposing a “Planet of the Apes” situation or suggesting that animals be given the suitable to vote; quite, he was proposing what he known as “bodily liberty” in a single of the eight preserves within the North American Primate Sanctuary Alliance.

In an interview with the nonprofit group My Dreams for Animals, he outlined bodily liberty: “Our cases are not about whether they are being treated well or ill in captivity — they’re about whether they should be held in captivity at all.”

However the appellate courtroom dominated unanimously in opposition to the notion that Tommy the chimp be given authorized standing as an individual, just like the protections granted firms, holding that, “unlike human beings, chimpanzees cannot bear any legal duties, submit to societal responsibilities or be held legally accountable for their actions.”

“In our view,” the courtroom mentioned, “it is this incapability to bear any legal responsibilities and societal duties that renders it inappropriate to confer upon chimpanzees the legal rights.”

Across the similar time, habeas corpus writs filed by the Nonhuman Rights Venture on behalf of three different chimpanzees in New York State additionally misplaced within the courts, though Stony Brook College returned the animal it was finding out to the New Iberia Analysis Heart in Louisiana.

Tommy was featured in “Unlocking the Cage” a 2016 documentary in regards to the Nonhuman Rights Venture directed by Chris Hegedus and D.A. Pennebaker. In response to some sources, he additionally appeared with Matthew Broderick within the 1987 movie “Project X.”

Mr. Smart instructed that eight different species may deserve the identical rights as chimps:gorillas, orangutans, bonobos, Atlantic bottlenose dolphins, African grey parrots, canine, honeybees and African elephants (together with one at the Bronx Zoo, whose authorized standing his group unsuccessfully challenged).

He cited a check carried out on nice apes whose faces have been dabbed with a purple dot. Once they appeared within the mirror, they reached for the dot on their faces, not within the reflection, indicating a way of self.

The notion of nonhuman animal rights has perturbed quite a few authorized students, distinguished amongst them Richard A. Posner, a former federal decide who taught at the College of Chicago.

“If we fail to maintain a bright line between animals and human beings,” Mr. Posner once said, “we may end up by treating human beings as badly as we treat animals.”

Different students disagree. Laurence H. Tribe, a professor emeritus at Harvard Legislation Faculty, mentioned in an e mail that Mr. Smart “will be remembered well beyond our time as one of the most farsighted and influential pioneers in the history of animal rights and animal welfare.”

“Steve’s writing, litigation strategy and organizational energy have taken our efforts to protect nonhuman animals from unspeakable wrongs to a new and promising level,” Professor Tribe added.

Martha C. Nussbaum, a thinker and professor of legislation and ethics at the College of Chicago, mentioned of Mr. Smart that she “disagreed with his theoretical approach but respected him greatly and supported his practical efforts.” Up to now, Professor Nussbaum mentioned by e mail, these efforts on behalf of chimps and elephants “have persuaded only dissenting judges, but that is the first step toward persuading a majority.”

Steven Mark Smart was born on Dec. 19, 1950, in Baltimore to Selma (Rosen) Smart, who managed the family, and Sidney Smart, a advisor to NATO.

He earned a Bachelor of Science diploma in chemistry at the School of William & Mary in Williamsburg, Va., in 1972. His involvement within the campus antiwar motion sparked a priority for social justice and led him to review legislation at Boston College, the place he earned a level in 1976.

In 1980, after a good friend gave him a replica of “Animal Liberation: A New Ethics for Our Treatment of Animals” (1975), by the Australian thinker Peter Singer, Mr. Smart was remodeled from an unfulfilled private harm and prison protection lawyer right into a fervid animal rights crusader.

He initially defended particular person animals, together with canine condemned to dying for attacking people, and was the president of the Animal Authorized Protection Fund from 1985 to 1995. He then based the Heart for the Enlargement of Basic Rights, which turned often called the Nonhuman Rights Venture.

Along with Siena Smart, his baby from his marriage to Debra Slater, which resulted in divorce, Mr. Smart is survived by his spouse, Gail Worth-Smart; a daughter, Roma Augusta, from his first marriage, to Marylou Masterpole, which additionally resulted in divorce; a son, Christopher, from his marriage to Ms. Slater; and a brother, Robert. He’s additionally survived by Yogi, a Yorkshire terrier-Maltese combine, whom he described as his canine companion.

(Tommy, the chimp, is believed to have died in 2022 in a zoo in Michigan.)

Contemplating his upbringing, Mr. Smart was an inconceivable champion of animal rights. He recalled that his mom “was always serving meat for meals” and wore a mink coat. He had canine and goldfish as pets, he mentioned, however as for his relationship with different animals, “I never really had any contact with them except with respect to eating them.”

By the point he was 11, although, he was so appalled at how chickens have been crammed into cages at a farmers’ market that he wrote to a state legislator to complain. He later turned a vegetarian and stopped carrying leather-based.

“I try to respect nonhuman animals,” he advised The Occasions in 2002. “I don’t eat them. I don’t wear them. I try to avoid being involved in the abuse of them. But you do grow up with certain things. Sometimes, I’ll be walking on a street and I’ll smell roast beef; I’ll simultaneously feel attraction and repulsion.”