Background: Advocacy is one of the most important institutions that can play a constructive role in the process of achieving justice. The presence of a lawyer in judicial trials will greatly facilitate the discovery of the truth and the prevention of encroachments and violations of citizens' rights. The necessity and importance of the right of defense have made it possible for advanced legal and judicial systems to view it as an important part of a fair trial to provide the necessary background for lawyers to perform their missions at all stages of the proceedings. Therefore, the presence of defense counsel during the proceedings is one of the most important and basic rights of the defendants and, in this respect, is particularly important in criminal matters. Therefore, the present study has attempted to examine the legal and ethical foundations of lawyer involvement in the judicial process.
Conclusion: The presence of a lawyer in the criminal justice process is justified on a legal and ethical basis. The legal basis of the right to choose a lawyer in the criminal procedure process has justice based and utility approaches. In the (justice-based approach), the participation of the lawyer guarantees the defendant's fair trial and fair trial. But under the (utilitarian approach), the participation of the lawyer in order to prevent the diversion of justice, to prevent the arbitrariness of those involved in the criminal justice system, to speed up the process of justice and to secure legitimate liberties, can be justified. But the ethical principles of the right to choose a lawyer in the criminal proceedings; In order to prevent delays in the proceedings, non-discrimination between designated attorneys and reciprocal and subjugation attorneys, the statement of facts to the client while justifying the subject matter and the secrecy of the client's statements can be justified.