What does Atticus do during his closing argument that astonishes Scout and Jem? Why do you think he does this?

In Chapter 20, Scout and Jem witness Atticus do something he's never done in front of them before. Atticus loosens his tie, unbuttons his collar and vest, then takes off his coat. Scout and Jem are both shocked and have no idea why Atticus is undressing in the middle of the courtroom. Scout says Atticus then casually addresses the jury "as if they were folks on the post office corner" (Lee 124). Atticus' "odd" behaviors are simply an attempt to seem relatable to the jury. Atticus loses his formal appearance and language in an attempt to appeal to the jury. He understands the jury is made up of staunch country folks who are deeply prejudiced and have an aversion to lawyers who defend African Americans. Atticus "undressing" and speaking informally may make the jury seem more open to his closing arguments. Unfortunately, the jury does not heed Atticus' closing remarks and finds Tom Robinson guilty.