After the US Supreme Court overturned the convictions in Powell v. Alabama (1932), Leibowitz was brought into the case by the International Labor Defense, an affiliate of the Communist Party of the United States.
[citation needed] After reading the record of the first trials and becoming convinced of the defendants' innocence, Leibowitz accepted the ILD's offer.
Leibowitz quickly became an object of loathing around Decatur when he opened his defense of Haywood Patterson, the first defendant to be retried, by challenging Alabama's exclusion of blacks from the jury rolls.
Local hatred of Leibowitz grew uglier, as death threats were made against him[5] after his tough cross-examination of the alleged victim Victoria Price.
The famous photo above was widely distributed to show the extent to which Leibowitz and these defendants had to be protected by the National Guard to keep the mob away from them during the Decatur trials.
Speaking before enthusiastic audiences sometimes numbering in the thousands, he promised to take guilty verdicts to the US Supreme Court and back until Alabama finally gave up: "It'll be a merry-go-round, and if some Ku Kluxer doesn't put a bullet through my head, I'll go right along until they let the passengers off."
After guilty verdicts and death sentences were handed to Patterson and Norris, a battle for control of the case ensued between Leibowitz and the ILD.
The Supreme Court again reversed the defendants' convictions in Norris v. Alabama, a decision that Leibowitz called a "triumph for American justice."
He met on death row several times with Bruno Hauptmann, the German immigrant convicted of kidnapping Charles Lindbergh's baby, in the hopes of convincing him to reveal details of the crime.
In early 1937, after a series of secret meetings with Thomas Knight, Leibowitz reluctantly agreed to a compromise, which would result in the release of four of the Scottsboro Boys and allow prosecutions to again go forward against the others.
In June 1937 he undertook the representation of Robert George Irwin, a former mental patient who was accused of murdering pulp magazine model Veronica Gedeon, her mother, and a roomer in New York City during Easter Weekend.
Early in trial, Leibowitz negotiated a plea bargain under which Irwin avoided the death penalty but would remain in custody for the rest of his life.
When Leibowitz reached the age of 70, he was subject to mandatory retirement unless a board of his fellow judges certified him as fit for continued service.
"What an intelligent, far-sighted humane administration from top to bottom," wrote the 65-year-old Leibowitz after had visited the Soviet Union: "In serving out his term of punishment the prisoner retains a feeling of dignity."
What Leibowitz had been shown on 31 July 1958 was not a strict regime penal colony but the "minimum security" prison at Kryukovo, where inmates were given an opportunity to learn the trade of their choice, and their wives could come and stay for several days.
An endowed law professorship of trial advocacy at Cornell, once held by renowned lawyer, judge, and lecturer Irving Younger, is named after Leibowitz.