This should be 2-3 pages, double spaced in Arial or Times New Roman font.
You should be writing all the events of the trial that YOU think YOUR CHARACTER would find important or interesting. The idea is to see how well you can "get inside someone's skin and walk around for a while" like Atticus says.
Your FINAL MOCKINGBIRD TEST is also on MONDAY.
Check out Sparknotes.com to brush up on your Mockingbird skills, and don't forget to review your quizzes and notes.