Rather than writing a continuous prose, think of this as a diary - You could make it start from the beginning of being in prison, and then as time goes by until (perhaps) you are finally set free.
So - first entry - Shut in this cage, anger at the judge, despair about future;
second entry - how long have I been here, how much I miss my family, how awful is the food, how boring the life; third entry - now time is crawling, it is months since I saw that outside world, my clothes stink, my hair is growing long, and so on
Just an idea.
Student or Learner