In the predawn hours of Oct. 23, a team of Hogan Lovells attorneys gathered in the firm’s Washington, D.C., office to await the outcome of their latest push to stave off the execution of convicted mass murderer John Errol Ferguson.

With Ferguson set to die by lethal injection in the bowels of a Florida prison at 6 p.m., the lawyers had prepared a dizzying array of filings and appeals that they hoped would spare the life of their longtime pro bono client. And though several of their strategies had already failed by the time the clock ticked past the scheduled execution time, the warden had paused the proceedings as the night wore on. At 11 p.m., 19 hours after they started their day, the phone rang one more time.

The call was from the U.S. Supreme Court, which was weighing the same argument the Ferguson team has made since taking the case in 1987: that the Eighth Amendment’s cruel and unusual punishment clause made it unconstitutional to execute their mentally ill client.

Hogan appellate partner Cate Stetson picked up the phone and listened to the Court’s darkly nicknamed “death clerk” on the other end of the line, then gave her 30 assembled colleagues a reassuring thumbs-up. Ferguson would not be executed—at least not yet.

“There was probably a minute or so of utter joy and relief,” says Des Hogan, a Hogan Lovells appellate partner working on the case, “followed quickly by a feeling of resignation that this fight isn’t over.”

The Supreme Court had affirmed a U.S. Court of Appeals for the Eleventh Circuit decision issued just hours earlier staying the execution based on a Florida federal district court’s issuance that same day of a certificate of appealability. Without taking sides, the lower court had acknowledged that Ferguson’s case presented significant constitutional issues that needed to be addressed. The entire appeal had flown through the courts in a matter of hours, with the lawyers compiling years’ worth of knowledge into filings written collectively in their D.C. war room.

Ferguson, 64, is undeniably a killer. Between 1977 and 1978, he participated in the murders of eight people—including a teenage girl whom he also raped—and the attempted murders of others. He is also, according to his lawyers, a diagnosed paranoid schizophrenic who for years has suffered from delusions that he is the “Prince of God” who will one day return to purify the earth. Raised in an abusive home, he first began to show signs of mental illness when he was 21 after being shot in the head during an altercation with a police officer. Following the shooting, Ferguson was consigned to an institution for the mentally ill. Psychiatrists there recommended that he be kept confined because of his homicidal tendencies. Despite those warnings, he was released and began his violent rampage. Two juries sentenced him to death. (Two other defendants convicted in six of the murders have already been executed in Florida).

Hogan Lovells lawyer Barrett Prettyman, now of counsel in the firm’s D.C. office, took the case on in 1987 through a referral from the American Bar Association‘s post-conviction project. While Prettyman continues to review every filing made in the case, today, Hogan partners Christopher Handman, Pat Brannan, Hogan, and Stetson, along with associates Lindsay Breedlove, Sarah Cummings, Marisa Cruz, Katie Marshall, Ben Lewis, Elizabeth Jose, and Erica Knieval, keep the case moving forward. Collectively, Hogan Lovells lawyers and staff have logged at least 31,000 hours—the equivalent of three and a half years of work—on Ferguson’s behalf. They don’t try to downplay Ferguson’s crimes and express no qualms about representing someone with such a violent past.

“You have to really look at it the way the Supreme Court looks at it,” says Hogan. “It is unconstitutional and there is no purpose served by killing someone who is mentally incompetent.”

Lawyers for the state of Florida insist that Ferguson is competent and hasn’t shown any signs of schizophrenia since being imprisoned. The state’s lawyers also say in court filings that Ferguson has “a significant history of feigning mental illness to avoid legal jeopardy” and that he spoke lucidly about his crimes and possible execution during several interviews with state-appointed doctors. One commission found that “For 90 minutes he engaged in regular conversation with us. He understood every question we asked him. He gave coherent logical responses. His speech was normal,” according to a court filing submitted by the state. Most recently, the Hogan Lovells team says, the state cited Ferguson’s acknowledgement that an execution date had been scheduled as evidence of his competency. A spokesman for Florida attorney general Pam Bondi said the office can not comment on pending matters.

Florida Governor Rick Scott prompted the latest round of appeals when he signed Ferguson’s death warrant on September 5—an act that effectively set the killer’s official execution date for the first time since he was placed on death row. About seven weeks later, on October 20, the Hogan Lovells lawyers thought they got the break they were looking for when U.S. district court judge Daniel Hurley in West Palm Beach stayed Ferguson’s execution. Within 72 hours, however, the Eleventh Circuit had reversed Hurley’s decision, leaving the execution scheduled for October 23.

While most of the Hogan lawyers working on the case convened at the D.C. office early that Tuesday, Brannan and Handman got on the first available flights to Florida to be with their client as he prepared to make his way to the death chamber so that they would be on hand to witness the execution should it in fact proceed.

For Brannan, that meant barreling down a highway in Maine to make it to the airport in time for a 6 a.m. flight, frantically emailing with Ferguson’s supporters along the way. Once at the prison, officials there gave her less than a half-hour to spend with Ferguson before they set about readying him for the execution. “Someone,” she says, “needed to look him in the eye and say, ‘I’m here for you.’”

Meanwhile, by the time the Hogan Lovells lawyers arrived at the D.C. office at 4 a.m., they had three certification petitions pending before the Supreme Court, as well as a federal habeas corpus claim in Miami federal court. At issue in that filing was their argument that Florida’s highest court had misinterpreted Supreme Court precedent from 1986 and 2007 barring mentally incompetent criminals from being put to death.

“To be candid, I was hopeful the U.S. Supreme Court would grant cert, even though cert is extremely rare, less than one percent,” says Hogan, who helped lead the efforts in D.C. that day along with Stetson. “The constitutional problems were so great, I thought it would catch their attention.”

Instead, over a period of two hours that afternoon, the Court rejected all three cert petitions. “It was incredibly deflating,” says Hogan (who is unrelated to the Hogan responsible for half of his firm’s name).

It was already 5 p.m. by the time the Supreme Court denied those petitions, and the district court case had become Ferguson’s last hope. Over the course of the next several hours, the lawyers pushed the case up the appellate ladder until the Supreme Court’s phone call came.

Meanwhile, 750 miles to the south, Handman and Brannan waited in the prison chapel for nearly six hours without knowing the fate of their colleagues’ efforts to have the execution stayed.

At 11:30 p.m., prison officials entered the chapel and told the dozen or so people waiting, including the families of Ferguson’s victims, “Okay, we’re going.”

As Handman recalls: “There was this odd ambiguity: Are we going to see an execution or going home?” As the prison staff clarified the remark, Handman and Brannan learned that the last-minute legal scramble had succeeded.

In the two months since that dramatic day, Handman and his Hogan Lovells colleagues have filed briefs with a three-judge Eleventh Circuit panel restating their case. After presenting oral arguments in November, the team is waiting for the panel to rule.

Brannan says the case will weigh heavily on her until that ruling comes. “As a lawyer, we’re responsible for these systems,” she says. “We’re accountable for them. We say people have legal protections available to them, and that the government can’t do terrible things to people without it being right. We’ve really been forcing those issues. … This isn’t a monster; it’s a human being. How we deal with that is a huge measure of who we are as a people.”

Prettyman, too, says the case continues to consume him. “It’s not an exaggeration to say it’s always on my mind,” he says. “Because a life is at stake.”