In 1987, Timothy Tyrone Foster, an 18-year-old black man from Georgia, was convicted and sentenced to death for the murder of a 79-year-old white woman named Queen Madge White.

On Monday, the Supreme Court invalidated Mr. Foster’s conviction and sentence because prosecutors had struck every black prospective juror at his trial — a violation of his constitutional rights. The ruling sends the case back to the Georgia courts, where the state may choose to retry Mr. Foster.

This was clearly the correct result. The prosecutors in Mr. Foster’s case kept notes that served as a remarkably explicit road map of how to discriminate in jury selection. For example, they highlighted the names of black prospective jurors on one list with a “B” and, on another list, ranked them against one another, in case “it comes down to having to pick one of the black jurors.”

Those notes were locked away in prosecution files for nearly 20 years, until lawyers for Mr. Foster obtained them through a state open-records law. Before then, the prosecutors got away with lying about their motivations thanks to Georgia courts that looked the other way. Even after the notes were revealed, prosecutors continued to concoct far-fetched explanations for their behavior.