回複：哦，謝謝分享你的知識，如果沒看見犯罪，但被警察問同學名字，必須回答嗎？

It is a judgment call. Depends on the state law and whether the stealing is a grand theft or petty theft, you may have an obligation to answer the question. Remember 5th Amendment is crime specific and you do not have its protection under such circumstances as a witness.