Leopold and Loeb confessed to a heinous murder. Clarence Darrow argued for mercy.

Nathan Leopold had planned to visit Paris in the summer of 1924. Instead, he and Richard Loeb found themselves behind bars and on trial for the murder of Bobby Franks, their neighbor in Kenwood, an enclave of Chicago’s wealthy Jewish families.

He might have thought the murder would provide him with a little extra spending money in France. He and Loeb demanded a $10,000 ransom from Franks’ parents in a note signed: “Yours truly GEORGE JOHNSON”.

Instead, the typed letter provided another key piece of evidence for law enforcement, whose case quickly came together with murder charges against Loeb and Leopold. The horrific crime that captivated Chicago and beyond was quickly followed by legal proceedings that proved equally gripping, culminating in an eloquent closing argument for the defense that remains a touchstone for courtroom oratory.

Loeb and Leopold’s lawyers initially pleaded not guilty on behalf of their teenaged clients and asked to have both men examined by an impartial commission of psychiatrists, at the time known as alienists. They had been seen by the state’s psychiatrists, and the trial looked to be a debate between rival takes from the men of science.

Leopold was fascinated by Friedrich Nietzsche’s theory of the übermenschen, a higher order of “supermen.” He tutored Loeb in his deduction from the German philosopher’s concept: If they committed a perfect murder, it would make them supermen, somehow immunized against moral judgment. Those beliefs became an argument for the defense.

“Leopold lives in a different world than you or I,” the famed lawyer Clarence Darrow told a reporter when the alienists filed their reports. “In his mind he had built a wall, which shuts him from the conventionalities and makes him the superman.”

“He does not believe in the laws that rule us, and the police are but obstructions which might stand in the way of living the life he has built,” Darrow said.

Darrow had been hired somewhat reluctantly by Loeb’s father, a wealthy lawyer who had been an executive with Sears, after friends touted Darrow as the best defense attorney his son could have. Darrow was a dropout from Jacob Loeb’s world, having given up corporate law to defend Eugene Victor Debs, a trade union organizer, when Debs faced charges in connection with the Pullman Strike of 1894.

Darrow became known as the champion of lost causes. Admirers didn’t know what to make of his decision to take on the defense of Loeb and Leopold, but while he opposed the death penalty for being frequently applied to poor defendants who were inadequately represented, his antipathy toward capital punishment in general ultimately carried the day.

Overcoming his initial hesitation, Jacob Loeb had gone to Darrow’s home in the Midway Apartments. Told Darrow was sleeping, Loeb barged his way in to see the lawyer and got down on his knees.

“Save their lives,” he begged. “Money’s no object.”

Despite their wealth and connections, public opinion was solidly against Loeb and Leopold, giving them the underdog role Darrow relished. He was also motivated at least in part by cash-flow problems. “I knew I’d get a fair fee,” said Darrow, a high earner and free spender. The Bar Association said Darrow and a co-consul should split the $125,000 payment.

Some figured the trial would hinge on an insanity defense. In Illinois, the legal definition of insanity was a defendant’s inability to understand the charges he faces. Acting or talking crazy didn’t count, and Cook County State’s Attorney Robert E. Crowe said his psychiatrists would testify that Loeb and Leopold were in full possession of their mental faculties.

Then Darrow made a surprise tactical move on July 21.

“We withdraw our plea of not guilty and enter a plea of guilty,” Darrow told Judge John Caverly.

By entering guilty pleas, Darrow didn’t have to persuade 12 jurors to spare his clients the hangman’s noose. In a trial’s sentencing phase, the judge has the ultimate say.

And Darrow knew the mountain of evidence against Loeb and Leopold was overwhelming. Elizabeth Slattter, Mrs. Leopold’s second maid, testified to seeing a typewriter in the Leopold home with a typeface that matched what could be seen on the ransom letter. Fellow students testified to using the typewriter in a cram session with Leopold.

Bobby Franks’ body had been found in a drain in a forest preserve at 118th Street in the far southeast corner of Chicago. A witness found eyeglasses near the body. While initially thought to belong to the victim, an oculist with the Almer Coe Optical Co. said he made glasses for Leopold that matched the pair found on the scene.

Leopold, who gave bird-watching classes in the forest preserve where the body was found, was questioned by the police. He denied the glasses were his and said that he and Loeb were out for a car ride the day Franks was abducted. But Leopold’s chauffeur told the cops the car Leopold said they were joyriding in was in the garage that day.

Confronted with those discrepancies, Loeb and Leopold gave confessions, portions of which were read at the trial. It drew a mass of spectators that Judge Caverly could barely fight his way through. The hearings drew people from around the country as well as Canada and Mexico, the Tribune reported.

State’s Attorney Crowe set up what a Tribune headline writer dubbed an “insanity school” in an effort to prove that Loeb and Leopold were sane and eligible for the death penalty. For two hours a day, the state’s physiatrists taught prosecutors how to “’boil down the evidence’ (so) the average layman of the jury will be able to interpret it in his common sense sort of way.”

Darrow also called psychiatrists — over the prosecutor’s objections — to explain his clients’ twisted thinking. While Crowe was combative, Darrow cultivated the look of a country lawyer, with rumpled suits and shaggy hair, and referred to his adversary as “my friend, Attorney Crowe.”

After the evidence had been presented, Darrow addressed the judge, speaking for 12 hours over two days.

“Your honor stands between the past and the future. You may hang these boys; you may hang them by the neck till they are dead. But in doing it you will turn your face toward the past,” Darrow said. “I am pleading for the future.”

His eloquent plea had the desired effect. Loeb and Leopold were sentenced to life in prison.

In 1936 Loeb was killed in the Stateville Correctional Center by an inmate he reportedly had propositioned.

Leopold was pardoned in 1958 and settled in Puerto Rico, where he married, received a master’s degree and taught, and continued his ornithological pursuits. He died in 1971.

Writer Meyer Levin told their story in in a 1956 novel, “Compulsion,” and a movie adaptation came out a few years later. After that, the crime and Darrow’s courtroom performance, while still kept alive in legal circles, largely faded from public view.

Illinois abolished the death penalty in 2011, eight years after Gov. George Ryan commuted the sentences of all those on death row. The 100th anniversary of the crime is an opportunity to remember Darrow’s words as he sought to save two men from the gallows.

“I am pleading that we overcome cruelty with kindness and hatred with love,” Darrow said. “I was reading last night of the aspiration of the old Persian poet, Omar Khayyam. It appealed to me as the highest that I can envision. I wish it was in my heart and I wish it was in the heart of all, and I can end no better than to quote what he said:

“So I be written in the Book of Love,
I do not care about that Book above.
Erase my name or write it as you will,
So I be written in the Book of Love.”

Have an idea for Vintage Chicago Tribune? Share it with Ron Grossman and Marianne Mather at rgrossman@chicagotribune.com and mmather@chicagotribune.com.