“There are thousands of people like Lyle and Erik who don’t have the celebrity, don’t have the personality, and don’t have the good fortune of supportive family, to lift their case up,” said Michael Romano, one of their lawyers.

Mr. Romano was an unlikely addition to the brothers’ legal team. Not that he didn’t believe the brothers, who murdered their parents more than three decades ago in their Beverly Hills mansion, had been in prison long enough.

But Mr. Romano has devoted his career to representing people serving life sentences for lesser crimes under California’s Three Strikes law, seeking to persuade courts to reconsider their sentences. Most of his clients are poor and Black or Latino. Yet many, like the Menendez brothers, suffered from childhood sexual abuse or other trauma.

So, during a prison visit with the Menendez brothers, Mr. Romano brokered a deal: If they ever walked free, they would speak out on behalf of other inmates who are not famous.

“I want them to say, when they walk out of prison and there are hundreds of microphones in front of them, to say, ‘We’re grateful but there are thousands of others behind us,’” said Mr. Romano, who teaches at Stanford Law School and runs its Three Strikes Project.

Last year, a new law went into effect that gives judges the independent authority to review virtually every conviction. “Almost everybody in prison is eligible for reconsideration,” Mr. Romano said.

So far, the number of people resentenced under that law are “minuscule,” he said, but the eligibility is “enormous.”

Mr. Romano hopes the Menendez case will provide judges with “permission to say, ‘Oh, no matter how notorious the case, no matter how gruesome the crime, it makes sense to go back and revisit these defendants and see if the sentences should be adjusted.’”