In the annals of the Supreme Court, the case of United States v. Shipp is an anomaly. Brought in the first decade of the 20th century, the Shipp case is the only time the court conducted a criminal trial, with justices serving as jurors.

But a case that history largely ignored is looking more and more like a landmark. The Shipp case was one of the first times the justices actively stood up on behalf of African Americans. The court left an evidentiary record that has become the basis for an inspiring act of racial healing. The Black and white communities of Chattanooga, Tenn., are working together to mark the site of a lynching in the heart of the city and at the heart of the case. Years of effort will culminate in the dedication of a memorial on Sept. 19.

In a time of mistrust along racial lines, the initiative in Chattanooga is a model for other communities. It demonstrates that agreed-upon facts can be a precursor to recovery. It couldn’t have existed without United States v. Shipp.

The story of the Shipp case begins in January 1906. That’s when Nevada Taylor, a young white woman, was raped in a Chattanooga cemetery. The crime provoked a frenzied reaction, putting pressure on the local sheriff, a proud Confederate veteran named Joseph Shipp, to identify and apprehend the rapist. The search had turned up a piece of leather. Upon the offering of a $375 reward for information leading to an arrest, a white man claimed to have seen a Black man milling around the cemetery, twirling a piece of leather shortly before the crime. He identified Ed Johnson as the man at the scene. Seizing on this shred of evidence, Sheriff Shipp arrested and jailed Mr. Johnson.

The rush to judgment continued through the trial. There were numerous witnesses who could say that they’d seen Mr. Johnson elsewhere during the time of the attack. And when asked to identify her rapist, Ms. Taylor said she believed that it was Mr. Johnson. But she declined to make a definitive identification. Taking the stand a second time, under a demand that she swear “in God’s name” that Mr. Johnson was the man who assaulted her, Ms. Taylor only reiterated that she believed that Mr. Johnson was her attacker. A juror shouted out a threat: “If I could get at him, I would tear his heart out right now.” Judge McReynolds failed to remove the juror, and Mr. Johnson was convicted and sentenced to death.

Two Black pioneering lawyers — Noah Parden and Styles Hutchins — led Mr. Johnson’s appeals. In an attempt to stop an unfair execution, Mr. Parden made a frantic journey to see the Supreme Court justice designated to hear emergency appeals from Tennessee, John Marshall Harlan. Fortunately, Justice Harlan was also the lone dissenter in Plessy v. Ferguson, the case that advanced the separate-but-equal doctrine.

Over two decades, Justice Harlan had failed to persuade a single colleague of the injustices being visited on African Americans. States’ violations of Black defendants’ rights were more a norm than an aberration. But the Supreme Court had resolutely looked the other way. For Justice Harlan, Mr. Parden’s arrival was a rare opportunity. Here, finally, in his capacity overseeing the Sixth Circuit, was a chance to order a federal review on his own.