The ground of nullity of the arbitral award for lack of reasoning pursuant to Article 829(1) n. 5 of the Code of Civil Procedure must be understood in a strictly literal sense and exists exclusively where the reasoning is entirely absent, or is so deficient as not to allow an understanding of the logical process followed by the arbitrators and an identification of the ratio of the decision adopted, and may not be invoked in relation to alleged deficiencies or errors in the assessment of the evidence adduced in the proceedings.
The complaint against the arbitral award that, although formally raised under Article 829(1) n. 5 of the Code of Civil Procedure, in reality challenges the erroneous assessment of the documents produced or the interpretation of the evidentiary findings by the arbitral tribunal, is inadmissible in that it concerns defects on the merits that are not among the exhaustive grounds of nullity provided for by the provision.
A decision of the arbitral tribunal founded on the findings of a court-appointed expert does not constitute a violation of the adversarial principle under Article 829(1) n. 3 of the Code of Civil Procedure, where the parties were afforded the opportunity to make observations on the draft expert report through their respective party-appointed experts and to make submissions on the expert's conclusions during the arbitral proceedings.
The alleged negligence of the arbitrators in the performance of their mandate, even if pleaded as the source of decisional errors, does not constitute a ground of nullity of the award challengeable under Article 829 of the Code of Civil Procedure, and may only form the subject of a separate action for professional liability.