1. According to Article 43 of the Lawyers Law of People's Republic of China (PRC), lawyers should abide by the law and respect professional ethics, and may not violate the law and professional ethics and damage the legitimate rights and interests of the parties. Among them, lawyers representing different interests may involve professional ethics principles such as independence, confidentiality and loyalty.
2. In China's criminal proceedings, the lawyer who represents the defendant in the investigation stage is generally considered to be involved in the "interests" of the case. Therefore, representing the plaintiff in the examination and prosecution stage may involve the professional ethics and legal provisions of lawyers, so it is impossible to defend the defendant in the investigation stage and the plaintiff in the examination and prosecution stage.