What is the significance of criminal defense? What are the functions and procedures of lawyers' defense in criminal cases?

Criminal defense is the work that lawyers, after accepting the entrustment of criminal suspects and defendants and obtaining the right of defense granted by them, put forward materials and opinions to prove that criminal suspects and defendants are innocent, lighter or exempted from criminal responsibility according to facts and laws, and safeguard the legitimate rights and interests of criminal suspects and defendants. Because the criminal suspect or defendant can't defend himself well for various reasons, lawyer's defense is of great significance for safeguarding the legitimate rights and interests of the criminal suspect or defendant and the correct implementation of the law. Lawyers have the right to intervene in the proceedings after the criminal suspect is taken compulsory measures or the defendant is summoned for the first time. Although this stage is not to exercise the right of defense, it is to prepare for the later exercise of the right of defense. Therefore, the revised Criminal Procedure Law also includes the lawyer's work in the investigation stage into the scope of defense. Lawyers of the same law firm may defend multiple defendants in the same criminal case, but the same lawyer may not defend multiple criminals who commit the same crime at the same time. In short, a defendant can hire two lawyers, but a lawyer cannot accept the entrustment of more than two defendants in the same case.