1. Relevance: During cross-examination, we should first check whether the evidence is relevant to the case, that is, relevance, including evidence unrelated to the case, which has no probative force and does not need to be cross-examined.
2. Legality: During cross-examination, it is necessary to check whether the source and acquisition method of evidence are legal, including that the source of evidence is illegal and the acquisition method violates the law, so the evidence has no probative force.