Hello. I don't know what evidence you mentioned in your previous assignment, which makes it impossible for me to answer your question efficiently. However, I will try to help you in the best possible way, showing you how to justify the chosen doubts.
you must justify the evidence based on the importance it has in the story you read. If you selected evidence where Douglass reflects on the importance of education, you can justify it by using the fact that education is liberating and would allow slaves to have enough knowledge to fight for themselves. If you used evidence about the misrepresentation that slavery imposes on society, you can justify how slavery is based on dominance and humiliation, generating results as depressing as the process itself.
This would solve the problem of false testimony and lying, but this could cause privacy issues. People would probably talk a lot less and read minds a lot more.
Explanation:
These are just some ideas, you are going to have to write this yourself, but this can help you get started.