If anyone sins in that he hears a public adjuration to testify, and though he is a witness, whether he has seen or come to know the matter, yet does not speak, he shall bear his iniquity.
#leviticus 5:1

You are not allowed to be silent about a crime. (A real crime, of course, not the made-up, politically motivated nonsense that fills most man-made law books.) If you have knowledge of the facts, you have a moral obligation to be a witness. #vayikra