In Harper Lee's Pulitzer Prize winning 1960 novel, the name of the solicitor is Mr. Gilmer. He is the prosecutor from Abbottsville who comes to town when court is in session. He is the prosecutor against Tom Robinson, and he and Atticus are friends. The way that he questions Tom Robinson in his cross examination upsets Dill because Dill thinks he is being mean to him. Scout thinks that Mr. Gilmer wasn't trying very hard in this case because she'd seen him be a lot rougher on other defendants, but it still bothered Dill nonetheless.
In Harper Lee’s 1960 novel To Kill a Mockingbird, the circuit solicitor, or prosecuting attorney, is Horace Gilmer. Scout’s references to Mr. Gilmer are frequently, simply, “the circuit solicitor,” or “solicitor,” as when she describes the scene, which comprises Chapter 17, in the courtroom for the trial of Tom Robinson: “The circuit solicitor and another man . . .,” and, again when she describes the contents of his table (“There was a brown book and a yellow tablet on the solicitor’s table . . .”) The “solicitor’s” last name, however, is finally revealed to be Gilmer, as when Scout describes the testimony of the county sheriff, Heck Tate:
“He was sitting forward in the witness chair, his hands clasped between his knees, listening attentively to the circuit solicitor. The solicitor, a Mr. Gilmer, was not well known to us. He was from Abbottsville; we saw him only when court convened, and that rarely, for court was of no special interest to Jem and me."
Later, in Chapter 18, we learn that Gilmer’s first name is Horace when the judge addresses him – or, more accurately, dresses him down – for making exaggerated objections to Atticus’ cross-examinations:
“Now let’s consider this calmly—” began Atticus, but Mr. Gilmer interrupted with an objection: he was not irrelevant or immaterial, but Atticus was browbeating the witness.
Judge Taylor laughed outright. “Oh sit down, Horace, he’s doing nothing of the sort. If anything, the witness’s browbeating Atticus.”
As Lee’s story, and Scout’s narration, progresses, we learn more about Horace Gilmer, who at first appears the prototypical, cold, passionless bureaucrat out to secure a conviction irrespective of justice. As with other of Lee’s characters, Sheriff Tate and newspaper editor Braxton Underwood in particular, Gilmer is, in fact, more committed to justice than the reader is initially led to believe. His questioning of witnesses, as Scout notes at one point, is entirely a matter of representing Maycomb County to the best of his ability (“Mr. Gilmer was doing his job, as Atticus was doing his”). Similarly, that Gilmer was tough on Tom Robinson during cross-examination was, as Scout pointed out to Dill, who was angered by the solicitor’s conduct, simply the way the system worked:
“That old Mr. Gilmer doin‘ him thataway, talking so hateful to him—”
“Dill, that’s his job. Why, if we didn’t have prosecutors—well, we couldn’t have defense attorneys, I reckon.”