what does a defendant need to show in order to prove in court they were unlawfully discriminated against by the police?

Chapter 3:
First, what does a defendant need to show in order to prove in court they were unlawfully discriminated against by the police? Second, why is this so difficult to show?
Chapter 4:
What is the “cruel hand”? Provide at least 2 examples from the text.
the link for the book is here
https://peacelawandjustice.files.wordpress.com/2013/12/newjimcrow-ch-1.pdf

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