Recently the public defender in criminal justice system has been discussed only in the context of the issue of judicial reform in Korea, especially the reform of the investigation structure. However, from a comparative legal point of view, the public defender is being implemented in major countries in order to realize the right of defense through the enhancement of defenders' assistance in criminal cases.

In order to elicit the necessity and validity of the public defender system, this study first examined the current State-Appointed Counsel System. It is alleged that the State-Appointed Counsel System has a difficulty in guaranteeing the quantity and quality of attorneys because of the poor treatment and expense of the lawyer. In order to solve this problem, Court-Appointed Counsel for indigent criminal defendants has been introduced but it has not only difficulty in guaranteeing the continuous and stable supply of the lawyer, also has the dependency on the court. In addition, the current system is based on the principle of helping criminal defendants, and is pointed out as an exception to the assistance of the accused in investigation. In other words, it is possible to partially defend the arrested suspects, but it is impossible to secure defense rights through the assistance of the defendants in the early stages of the investigation, such as the entire detention investigation or the prosecution before the prosecution.

As a result of examining the legal structure and especially the law and practice of the State-Appointed Counsel System, this study categorized the public defender type (model) of major countries into the nation-dedicated system, the legal-aided system, the universal aided system and the selective aided system.

Consequently, in order to solve the problems of the State-Appointed Counsel System, it is necessary to expand the scope of the public defender in criminal justice system to the stage of the suspects under investigation, and to consider the self-requisites of the suspects. At the same time, it is necessary to consider alternatives to the legislation on the perspective of independence and status of institutions, and the organization and functions of the public defender. However, in the case of model the nation-dedicated system, the new law should be presented as a form of enactment and the case of the legal-aided system should be presented as an amendment to the existing law such as LEGAL AID ACT. In particular, the LEGAL AID ACT, which should be amended as the legal-aided system model, we proposes a revision plan that clarifies the legal basis of the (criminal) duty lawyer system under the current program.