She's the attorney who helped spare the Unabomber from the death penalty, though Ted Kaczynski never forgave her for trying to make him look insane.
She saved Susan Smith's life, too, by convincing jurors that the vilified South Carolina mother who drowned her children was a fragile victim of sexual abuse who should not be executed.
In 20 years as a defense attorney, Judy Clarke has represented the most notorious murder defendants in modern American history, including Olympics bomber Eric Rudolph and Jared Loughner, who tried to assassinate Arizona Rep. Gabrielle Giffords and killed six others.
And each time Clarke has either negotiated plea deals in exchange for a life sentence or persuaded jurors to spare her client's life.
Now she is faced with what could be the stiffest challenge yet to that perfect record: keeping Boston Marathon bomber Dzhokhar Tsarnaev off death row.
"This is a very difficult one, no question about it," said Lesley "Lee" Coggiola, an attorney who worked with Clarke on the Smith case. Coggiola says she is worried that Tsarnaev may be the first client Clarke cannot save, because the government's evidence appears strong and Bostonians are so traumatized by the April 15, 2013, terrorist attack that jurors may be willing to buck the state's usual opposition to capital punishment.
A loss, Coggiola added, would come as a blow after a long career that has made Clarke one of the top anti-death-penalty attorneys in this country.
Tsarnaev is expected to be found guilty this week when the first phase of the trial ends. That's hardly a surprise given Clarke's admission during opening statements that Tsarnaev planted one of the twin bombs that killed three people and injured 260 more.
It's after the verdict — during the penalty phase — when Clarke's real challenge begins.
Using a legal strategy she has honed over many years, Clarke, 63, will try to portray the 21-year-old as a confused college student from a broken home, a loner manipulated by his more radicalized older brother, and most important to Clarke, a human life that should not be tossed away, even if he spends the rest of it in prison with no parole.
In court since early January, Clarke has shown no sign of worry, no indication that things are not going well. The tall, thin runner usually arrives to court wearing a rosy winter scarf and the face of optimism.
In pretrial skirmishes, though, she has lost on several key issues, including moving the case out of Boston. Nor has she been permitted to put on much evidence so far about the older brother, Tamerlan Tsarnaev.
During testimony, she has largely sat quietly in the courtroom next to Tsarnaev. She does not speak much to him, though. Instead, federal public defender Miriam Conrad and others on Clarke's team have largely handled the guilt phase of the trial.
Despite her famous client list, Clarke appears to care little about celebrity, routinely turning down media interviews, including for this story. She typically walks steadily past television cameras, even as other lawyers rush toward them.
In a rare interview with the Los Angeles Times in 1990 when she was a federal public defender in San Diego, Clarke said she drew motivation and inspiration from inside the courtroom. "I like to fight," she said. "I love the action. I like the antagonism. I like the adversarial nature of the business. I love all of that."
After representing Smith, Clarke became one of the nation's leading opponents of the death penalty. She has argued that Smith and her subsequent clients are not monsters, but instead broken, mentally ill victims themselves.
In 1994, Susan Smith strapped her two young sons into the family car and rolled it down the ramp at a lake. She claimed she was carjacked, but later confessed the story was a lie. Prosecutors said Smith, separated from her husband, wanted to kill the children because she feared her new boyfriend did not want the responsibility of a family.
Coggiola said it was this case that persuaded Clarke to make anti-death-penalty advocacy largely her life's work. Clarke highlighted Smith's sexual abuse as a child and the pressures of motherhood. She developed a strategy to present the defendant as a "whole person" who made one horrible mistake, Coggiola said.
"One of the things Judy has always been so good at doing is saying, 'You don't judge people by their worst day, or their worst event,'" Coggiola said.
It was a gamble. One of the jurors was the wife of the local police chief, recalled Tommy Pope, the prosecutor who was trying to persuade the jury to give Smith the death penalty. He described Clarke's attitudes about capital punishment as "intense," saying, "She was on a mission. A crusade to abolish the death penalty. One case at a time. One technicality at a time."
He recalled Smith giggling and playing tic-tac-toe in the courtroom when the jury was not there. When jurors were present, he said, Smith suddenly became somber and sometimes cried. He called it an "acting job," part of Clarke's effort to connect the jury to Smith's anguish.
"She started out as Susan the monster who killed her kids," Pope said. "By the time it got to the jury, they were seeing Susan as a victim. And that's Judy Clarke's play. That's what she seeks out."
The jurors gave her life in prison. According to Coggiola, they asked the judge if she could get mental health counseling behind bars.
Clarke was raised by conservative parents in North Carolina and as a child dreamed of becoming chief justice of the U.S. Supreme Court or the courtroom TV hero Perry Mason.
She also secretly nurtured a liberal side, voting for Democratic Sen. George McGovern for president. She graduated in 1977 from the University of South Carolina Law School, married a fellow lawyer, and threw herself into the law.
In the legal arena with capital murder defendants, her strategy has always been to work hardest in the pretrial phase, hunting for an opening for a plea bargain.
Kaczynski, the so-called Unabomber, was charged with sending explosives through the mail that killed three people and injured a dozen more. In 1998, with his trial approaching, he tried unsuccessfully to fire Clarke because she was working up an insanity defense without his permission.
He eventually pleaded guilty and accepted life in prison, primarily to prevent Clarke, whom the judge would not let him fire, from arguing he was mentally ill, according to a recent Vanity Fair article.
In the Tucson shooting, she won a plea bargain for Loughner's life when the court ruled he was mentally incompetent when he wounded Giffords and killed six others. He was clearly troubled; in one pre-trial hearing he leaped from his seat screaming and was subdued by U.S. Marshals. Sources in that case said Clarke often was afraid of Loughner and sometimes sat away from him in court.
In the Tsarnaev case, according to sources familiar with the talks, overtures were made to discuss a plea arrangement. But in the end prosecutors saw little reason to deal. Surveillance video and other evidence put Tsarnaev at the finish line of the race when the bombs went off. Instead the government has pushed to win its first death penalty case since Sept. 11.
Clarke's path to Boston, said Robert Dunham, executive director of the anti-capital-punishment Death Penalty Information Center, came when Conrad, the federal public defender, realized she needed help with Tsarnaev's case.
The bombing was the worst terrorist attack since planes crashed into the World Trade Center, Pentagon and a Pennsylvania farm field in 2001. Prosecutors quickly portrayed the Tsarnaev brothers as extremists bent on killing Americans. They've suggested that Dzhokhar Tsarnaev intentionally set his pressure-cooker bomb next to a family with small children, killing an 8-year-old boy and maiming his sister.
It was exactly the kind of challenge Clarke has thrived on in the past.
"She's brilliant," Dunham said. "Now they will have to change the picture of him from the prosecution's suggestion that he is a terrible monster. She has to help the jury come to see that they also have a young man who has some serious problems, but that he is a person too."