EXPERTIUS is the first Mexican AI and Law application. The system advices upon the determination of whether someone is entitled or not to a financial pension (under the so called “feeding obligation”), and upon the determination of the amount of that pension. EXPERTIUS is based on a multi-layered knowledge representation. At the first layer lies the so called heuristic or compiled knowledge needed to solve cognitive tasks. A set of cognitive tasks is associated to a set of decisions internal to particular procedural phases. A dialogical-confrontation structure supervenes on the decisions taken in the intermediate level.