mere coincidence.  Scout narrates,

In Maycomb, grown men stood outside in the front yard for only two reasons:  death and politics.

Sheriff Heck Tate tells Atticus that he is going to move Tom Robinson to the county jail the next day. 

Mr. Link Deas said, "Nobody around here's up to anything, it's that Old Sarum bunch I'm worried about...can't you get a--what is it, Heck?"

"Change of venue," said Mr. Tate.  "Not much point in that, now is it?"

Atticus will not back down from the men, saying that he could not refuse to defend him.  He tells Mr. Deas,

"Link, that boy might go to the chair, but he's not going till the truth's told....And you know what the truth is."

Later that evening, the children follow Atticus and find him sitting in one of his office chairs before the jailhouse door.  Scout and Jem also find four dusty cars coming from the Meridian highway, all in a line.  As the men approach Atticus, tension clearly rises.  The men almost whisper to him,

"You know what we want....Get aside from the door, Mr. Finch."

When Atticus tells the men that Heck Tate and his men are around somewhere, one of the men contradicts, saying that they have been tricked into going into the woods.  Then, Atticus says, "...that changes things, doesn't it?""

"It do," another deep voice said.

"Do you really think so?"

This is Atticus's challenge to the men.  But, Scout intervenes and diffuses the tension as she personalizes her address to Mr. Cunningham; he then becomes ashamed and tells the men to leave.

Chapter 21

In this chapter, Jem and Scout await the verdict, and the Reverend Sykes tells Jem,

"I ain't never seen any jury decide in favor of a colored man over a white man."

Chapter 28

Having created a false climax in this chapter, Harper Lee has Scout and Jem frightened as they walk to the school pageant; however, the threat is none as it is only Cecil Jacobs who appears.  Then, later in the chapter the children hear someone shuffling behind them. Suddenly, Jem lets go of Scout's hand and is jerked backwards; Scout's

toes touched trousers, a belt buckle, buttons, something I could not identify, a collar, and a face.  A prickly stubble on the face told me it was not Jem's.  I smelled stale whiskey.

After this, Scout sees someone carrying Jem, whose arm dangles unnaturally.  Of course, the real climax and greatest tension comes as Boo and Bob Ewell struggle.

In addition to the examples mentioned in the previous post, a crowd of Maycomb citizens congregated on Atticus' lawn two nights before the trial. In addition to Sheriff Tate, others present included Link Deas, Mr. Avery and Dr. Reynolds. The scene is told from Scout's perspective, and she stayed indoors and was not able to hear much about what was said. But Scout knew it must be serious.

    In Maycomb, grown men stood outside in the fron yard for only two reasons: death and politics. I wondered who had died. 

Scout was able to overhear a bit of Sheriff Tate's conversation, however. She learned that Tom would be moved to the county jail the next day, and that there might be trouble. Then she heard Atticus question the sheriff if he was " 'scared of that crowd...' " The tension became so strong that suddenly

Jem screamed, "Atticus, the telephone's ringing!"

When Atticus finally came inside, Jem revealed that he thought the group of men in the yard were a gang who had come for Atticus. Later, Jem revealed to Atticus that he was scared:

"Scared about Atticus. Somebody might hurt him."

There is tension and unrest in both the Finch household and the town.  I think this is important, as the story teller is greatly affected by both.

Starting in her own house, Scout begins to notice, with the arrival of Aunt Alexandra, that things are different.  Atticus seems to have less patience and time for her.  Jem is even distant, as if he too senses the stress that is affecting everyone.  Scout is young, so she definitely notices this tension but probably cannot name it, nor fully understand it.

Then, in Chapter 14, Scout reports in the very first line:

Although we heard no more about the Finch family from Aunt Alexandra, we heard plenty from the town.

It seems the entire town is talking about the trial - from the recognition of "his chillun" (meaning Atticus) to Scout hearing the word "rape."  The usual gossip of a small town has basically all turned on the same subject, and Scout not only notices it, but goes home to discuss it with her father.  This only furthers the stress at home and reinforces the tension.

Scout has already faced criticism from her own schoolmates concerning Atticus's decision to defend Tom. She and Atticus have both been called "nigger-lovers," and sister Alexandra believes Atticus's defense of Tom is " 'ruinin' the family.' " Mrs. Dubose's verbal attacks on Atticus are based on his taking the case, and Alexandra arrives in Maycomb in order to run the house while Atticus is busy with the case. As the trial neared,

... we heard plenty from the town... sometimes hear, "There's his chillun," or "Yonder's some Finches."  (Chapter 14)

But not everyone is upset with Atticus. Jem and Scout are treated with respect when they attend Cal's church with her; the congregation knows that their father has agreed to defend their friend, Tom. On the weekend before the trial, Atticus was met by concerned neighbors who were worried about Atticus's--and Tom's--safety. Sheriff Tate warned Atticus that Tom's move to the local jail might bring problems, and Atticus is forced to stand guard over Tom to protect him from the lynch mob that appeared. Virtually the entire county turns out on the day of the trial.

     It was a gala occasion. There was no room at the public hitching rail for another animal... The courthouse square was covered with picnic parties...  (Chapter 16)

And the children overheard more gossip about Atticus, learning for the first time that he had been appointed by Judge Taylor and that he had not taken the case on his own. For Maycomb, the trial of a white female victim and a black man accused of raping her was (as Miss Maudie had noted) like a "Roman carnival"--an event rarely seen in these parts.