In the Hungarian system of criminal procedure, several participants of the proceeding may provide activities aiming at the defence of the defendant (e.g. the prosecutor or even the defendant himself). My dissertation, however, shall focus on the activities of the defender based on delegation or recorded Power of Attorneys given, in consideration of the fact that almost without exception this personal group act as advocates in criminal procedures, furthermore, solely lawyers have the expertise necessary for the defence, and the “equality of arms” principle may only succeed completely through them.