How is waiting for the verdict similar to watching the mad dog scene?
Suspense! During the mad dog scene, we see Atticus using a skill that not many know he possesses. We watch the dog slowly turn back up the street and begin walking toward Atticus. Of course Jem and Scout have no idea what Atticus is doing (since they think he is more of a coward than he is), and we wait for the moment when Atticus finally pulls the trigger and drops the dog.
We have the same type of suspense during the trial. Atticus has displayed his lawyer skills to the best of his abilities - in fact, has even proved the Ewell testimonies false. We wait on the verdict because we know Atticus is right, but we also know that it would take a very strong show of bravery and conviction on the part of the jury to allow Tom to walk. Although we don't see the same success with the trial that we did with the dog, we do see how Atticus is able to stick true to his character and teach his kids a valuable life lesson.
To elaborate on this, Atticus' physical actions are paralleled: "Atticus put his foot on the rung of a chair and rubbed his hand slowly down the side of his thigh" (95) just before he shoots the dog. He performs the same gesture just before the jury enters (210). Perhaps this is what triggers Scout's memory of the event as she watches, waiting for the verdice.
I think that a case can be made that both are examples of the mockingbird. For instance, the whole town is a mockingbird that recreates racism and oppression. Atticus is the only one in the town the skill to even attempt to fight it. Atticus kills the mad dog with his amazing skill with a gun and his amazing understanding and human compassion make him the man most likely to have success with changing the song of the town (he is after all a Finch). When I teach this novel to the students one of their final questions is to argue that the scene where Atticus shoots the dog is in fact the climax of the entire novel--for if read symbolically, it is.