Legal analysis: depending on the specific situation. If it is approved by the court, it is effective. The lawyer's letter is issued in the name of a law firm. Opinions and opinions on some issues are the behavior of a unit and need to be stamped with the seal of the law firm. Whether the lawyer's letter is valid depends not on the authenticity of the lawyer's letter, but on whether the court approves it. Only the lawyer's letter approved by the court is valid.
Legal basis: Article 33 of the Lawyers Law of People's Republic of China (PRC). Lawyers who act as defenders have the right to meet criminal suspects and defendants in custody or under residential surveillance with lawyer's practice certificate, law firm certificate, power of attorney or legal aid letter in accordance with the provisions of the Criminal Procedure Law. Defense lawyers are not monitored when meeting with criminal suspects and defendants.