It's pretty improbable that a southern white jury would believe this claim however.
It's possible that due to Atticus' senility, we're not supposed to believe the claim that he got Robinson acquitted at all. He's clearly far enough gone that anything he says is...suspect at best.
The lengthy gap between the books actually puts the audience in the exact same position as Jean Louise. After so long of putting Atticus on a pedestal as an idealized equality crusader, we're suddenly presented with a much different image of him as a deeply flawed man, and have to come to our own conclusions in how to reconcile it.
Meta example: Seeing as the book received quite a few negative reviews, one has to wonder if Lee herself considered it a failure during her own lifetime. (Why else would a Pulitzer-winging author whose book was made into an film that won multiple Oscars keep a manuscript such a big secret?)
Well, it was actually her first novel, not a sequel- it was specifically rejected and reimagined as TKAM.
In TKAM, Atticus says that any White person who takes advantage of a Black person is trash. Over the years, many readers have interpreted this statement as a condemnation of the unfair social and legal advantages enjoyed by White people at the time, in which such a White person could be assured of getting away with his or her actions because there would be no way society — or the law — would ever side with a Black person. However, this book lends an uglier interpretation to Atticus' earlier statement. In The Reveal, Atticus states that Black people are "still in their childhood." Thus, what Atticus really meant in TKAM is that he is against taking advantage of Black people, not because of any legal or societal inequalities, but because he equates them with children, and he would similarly condemn an adult taking advantage of a small child.
For many (including many who went into the legal profession because of and/or named their sons after him), Atticus Finch essentially has a Face–Heel Turn by revealing that he is also a bigot with views little better than the villains in the original book. One wonders how many were unable to reconcile such a previously heroic character now not so heroic?
However, the above point, while brilliant in a meta sense, is also faulty. Much of the reason that Atticus is put on a pedestal in the first place is because of the events of To Kill a Mockingbird, which this novel very much contradicts in a way to where both stories cannot be set in the same universe. And Go Set a Watchman by itself really doesn't show much of Atticus in the past, in order to gain and justify that sense of putting him on a pedestal- which just further muddies the issue (of course, much of this is because of the book's Obvious Beta state).
