Abstract
This paper aims at reviewing both the concept of the conflict of duties in criminal law as well as the foundations for its solution. Regarding the former, this legal institution is defined as a collision of reasons for duty that cannot be cumulatively fulfilled. Their deontic nature is thus irrelevant. About the second issue, the argument is made that the solution of the collision involves a judgment set out to hierarchically arrange the colliding reasons, a judgment in which the conflict is understood from a formal point of view that is respectful with the autonomy and solidarity principles. The class or kind of duty, as a means of stating the weight of the obligation in view of the obliged party/beneficiary relationship, operates then as a tie-breaker rule in those cases where the comparison between the two beneficiaries of the competing obligations provides no significant normative difference. Therefore, the obliged party must only fulfill the reason of the superior obligation — the only duty which can be legitimized in the particular situation — or, when before a collision of equivalent reasons, they must comply with the disjunctive duty — aid one or the other — which the legal system imposes on them.
