Any forensic psychological expertise, regardless of its nature and degree of complexity, must be based on the observance of certain principles, on fundamental ideas that should be at the core of the professional conduct norms of those entrusted with the mission of organizing and conducting such an expertise. Whether viewed from the perspective of legal provisions related to forensic expertise or from the standpoint of the ethical codes of the psychology profession, or even when approached from both perspectives simultaneously, the principles considered constitute, de facto, the necessary source for implementing an efficient model of ethico-professional decision-making, a model that involves at least eight stages: (i) problem identification, (ii) determination of the ethical and legal expressions determined by context and circumstances, (iii) identification and implementation of ethical and legal resources, (iv) reevaluation of personal beliefs and values, (v) designing ways to solve the identified problem, (vi) projecting the consequences (positive/negative) that the methods of solving the identified problem could generate, (vii) designing and implementing the strategy and techniques for conducting forensic psychological expertise, and (viii) evaluating the results of forensic psychological expertise.