The burden of proof rests on the person who makes an allegation. (c. 1526 §1). The bulk of work in most ecclesiastical tribunals across the Catholic world is marriage nullity cases. Parties are required to provide proofs regarding their claim or their counter-claim. Therefore, proofs in marriage nullity trials comprise the means by which an assertion is established. Already with the submission of a petition introducing the case, the petitioner is required to indicate not only the facts upon which the assertion is made, but also the proofs that will be adduced to support the petitioner's claim. (c. 1504, 2º). The proofs either strengthen or weaken the petitioner's claim or the respondent's exception to it. This book addresses the norms governing the instruction of the case and the evaluation of canonical proofs thereof as stipulated in the Code of Canon Law and in Dignitas connubii. These norms are meant to enable the judge acquire the moral certainty regarding the probative value to be assigned to each proof. This book examines these procedural norms based both on jurisprudence and personal experience. It is highly recommended for all ecclesiastical judges and tribunal officials, parties in a case, canon law students and practitioners, civil law students and practitioners, and other interested persons.