The Texas Court of Criminal Appeals hears all death row appeals in the state. Cathy Cochran is one of nine judges on the court. This is the story of how one of Cochran’s 2004 death penalty rulings became de facto law. But the story actually starts far away from Texas, in the 1960s, when Cochran was an Army wife in Monterey, California.

“We lived right above Cannery Row when we were first married, and so I re-read all of Steinbeck when we lived there,” she recalls.

Cochran grew up in rural California; she loved how Steinbeck depicted the underbelly of her state. “He always has such good stories about the importance of connecting with people—realistic portrayals of human beings that were outside, at least for that time, of the general reading public,” she says.

People like Lennie Small, the protagonist of Steinbeck’s 1937 novella, Of Mice and Men. High school students have been meeting Lennie for decades:  He’s a big guy, strong, but mentally disabled.  Lennie loves little animals but often crushes them by accident.  His companion George tries to protect him, but they have a rough life as vagabond ranch hands.

“Lennie’s sort of the gentle giant,” Cochran says. “Not realizing what he was doing, not knowing the consequences” when he accidentally murders a woman at the end of the novel. “And I think that’s part of what was behind the Atkins Case as well,” the judge adds.

“The Atkins Case” is a 2002 Supreme Court ruling.

It says it’s unconstitutional to execute mentally retarded people — and yes, “retarded” is the term court used.  The Court ruled that such executions violate Eighth Amendment’s prohibition against cruel and unusual punishment. But the Court left the job of actually defining “retardation” up to the states.

After Atkins, many states adopted a clinical definition based on IQ and “adaptive deficits.” It’s similar to what a social worker would use to assess somebody for disability benefits.

But the Texas legislature could not agree on a definition. While it was trying to negotiate one, though, death row inmates started filing appeals, claiming to have intellectual disabilities. Texas does not like appeals to linger and delay executions, though. So the Court of Criminal Appeals decided to take one case and use that decision as a precedent for similar cases—a sort of working definition.

Cathy Cochran was the judge who wound up writing the opinion that became the working definition. It’s called Ex Parte Briseño. Judge Cochran says she was trying to reconcile scientific definitions of intellectual disability with state law. And while she was doing that, she thought of Steinbeck’s Lennie.

“Certainly we can all agree that somebody like Lennie from Of Mice and Men is exactly the sort of person that people would say, ‘Lennie should not be executed,’” she says.

In her 2004 opinion, Cochran wrote: “Most Texas citizens might agree that Steinbeck’s Lennie should, by virtue of his lack of reasoning ability and adaptive skills, be exempt” from execution.

But Cochran went on to write that Texas would also not want to exempt everyone who meets the social services definition of “retardation.” She set out seven factors –now referred to as “Briseño Factors”–for lower court judges and prosecutors to consider when they hear death row appeals.

“Things like: Is this someone who’s a leader or a follower?” Cochran explains. “Is this someone who can lie effectively and spin a good story and keep things straight? You can’t spin a good lie and keep it going if you can’t remember things for very long, if you’re not coherent, if you can’t tell a clear story.”

Cochran believes her ruling balances criminals’ claims of mental retardation against a Texas culture that encourages speedy executions. Critics say Cochran’s ruling is rife with stereotypes of people with mental disabilities. The first problem: using Steinbeck’s Lennie as a baseline.

“The character…is a person who I would say, on the face of it, was intended to describe someone with moderate to severe intellectual disabilities. Not someone in the mild end of the spectrum,” says Margaret Nygren, head of the American Association for Intellectual and Developmental Disabilities. She and other critics say it’s much harder to diagnose disabilities on the mild end of the spectrum. But those are precisely the people the Supreme Court intended to protect with the Atkins ruling: people who may be just disabled enough to have a terrible time in court.

“The social judgment may not be there,” Nygren says of such defendants. “They may not quite understand that the person interrogating them is being less than truthful…They may not be able to make eye contact. They may be so agreeable and wanting to please those around them that they are unable to successfully contribute to their own defense.”

In fact, it can be very difficult, if not impossible, to win a disability claim on Texas’s death row. John Blume, a law professor at Cornell University, has studied how Atkins appeals are handled in courts around the country.

“From reading the decisions,” in states like Texas, Blume says, “sometimes it’s frustrating to read it and see the lengths to which sometimes judges will go to, to have a person whom I think any rational clinician would say has mental retardation and say, ‘No no, they’re not.’”

Blume believes one person who probably wouldn’t pass Judge Cochran’s so-called “Lennie test” is Lennie himself.

“I mean, after he accidentally strangles the young woman, he tries to cover it up. That’s one of the factors the Briseño opinion cites as evidence that somebody doesn’t have mental retardation. They would look into the fact, “well, he worked. He worked as a farm hand. He was gainfully employed.”

And Blume is not speaking abstractly here. Texas death row inmate Marvin Wilson had an IQ of 61, putting him at the bottom one-percent of human intelligence; he was diagnosed with serious intellectual disabilities.

A court-appointed doctor testified that Wilson could barely read, write, or handle money. But a lower court ruled he “functioned sufficiently in his younger years to hold jobs [and] get a driver’s license.”

Attorney Lee Kovarsky represented Wilson. “The [lower] court invoked under one of the factors that the client was not mentally retarded because he was married and had a child, as if human love and reproduction was something that people with mental retardation are not capable of.”

Marvin Wilson was executed by lethal injection in August of 2012.

As Of Mice and Men ends, Lennie is hiding out in a grove of trees.  George finds Lennie before a vigilante posse can hunt him down. He tells Lennie his favorite story about their imaginary future together, one in which Lennie will be able to raise rabbits. Then George pulls out a gun.

“The reason George shoots Lennie is because he knows if he gets caught, [execution] is exactly what will happen to him,” says John Steinbeck’s son, Thomas Steinbeck. In 2012, he found out about the Texas ruling that cites his father’s work. Thomas Steinbeck says his father opposed the death penalty, and the younger Steinbeck issued a statement condemning the Texas courts.

“To judge anything based on a piece of fiction I think is a stretch,” says Thomas Steinbeck. “And I think it would’ve made my father extremely angry.”

His outrage does not faze Judge Cochran.

“I think [John Steinbeck] would be pleased that the world recognizes that Lennie is a gentle giant who is not morally culpable, and that people like Lennie, people who are not the worst of the worst…should never be subject to the death penalty even though they might have caused someone’s death,” she says.

Cochran admits she’s far more comfortable interpreting the law than writing it, and she wishes Texas lawmakers would get around to defining intellectual disabilities for death row appeals. But for now, or at least until the Supreme Court changes it, her ruling—including Lennie Small–is the law of the land in Texas.