When the suspect or the accused is charged in criminal cases and is superintended by the competent official. Having a defense lawyer in defending the charge is the primary right of the accused. This is the protection for the alleged offender or the accused according to the law of criminal procedure in every country. This thesis finds that the defense lawyer must carried on his duties and obligations in finding all sorts of evidence on behalf of his client. This is so because most of the accused, by themself, have no chance or have not ability in finding the fact to prove their innocent or to dispute the prosecution witness. The law of criminal procedure of the United States of America, which accept the importance of the defense lawyer's role, emphasize the defense lawyer's duties and obligations in fact findings. As a quasi-judicial officer, he has the duties and obligations to the public as well as to his client, that is, an attorney is an instrument or agency to advance the ends of justice. For that purpose, the law of criminal proceedings of the United States of America imposes the defense lawyer's duty for rendering an assistance to social justice or finding fact from every evidence in the stage of pre-trial and the stage of trial. The defense lawyer must present the matter with public responsibility for the impartiality of the parties in adjudication by the court. The study of Thai criminal procedure law reveals that the defense lawyer only have the right to render an assistance to their clients by meeting and counseling. The law does not confirm the defense lawyers' role to prove their clients' innocent or to discuss the evidence of prosecution. In order to solve this problem, the Code of Criminal Procedure Law must be amended by adapting the concept which give the authority to defense lawyer in finding the fact from the stage of pre-trial until the stage of trial in criminal case.
