The concept of reasonable inference plays a pivotal role in three major domains: uncovering the truth in modern offences such as cybercrimes and complex financial crimes; strengthening the judge’s customary knowledge in traditional and ḥadd offences; and assessing the credibility of claims throughout the adjudicatory process. To evaluate this concept, three categories of criteria are proposed: procedural criteria (legality, relevance, and admissibility), substantive criteria (inferential strength, sufficiency, and coherence), and methodological criteria (possibility of technical assessment and testability).Using a descriptive–analytical method and a comparative–critical approach, this study examines the conceptual gap and the absence of clear standards for reasonable inference in the Iranian criminal justice system. It demonstrates that although the notion appears in provisions such as Article 114 of the Criminal Procedure Code and Article 156 of the Islamic Penal Code, its inherent ambiguity has led to conflicting interpretations, discretionary decision making, and ultimately the weakening of the fundamental principle of presumption of innocence.In other legal systems, criteria such as “observable and explainable conduct,” “probable cause,” and “serious or consistent indicators” have been identified. The study concludes that without the formulation of transparent and binding standards, reasonable inference will remain a vague and contested legal construct. To address this issue, it recommends adopting a unified judicial guideline that precisely defines procedural and substantive criteria, and establishing mandatory benchmarks—such as a “minimum threshold of evidentiary sufficiency” and a “requirement of independent technical assessment”—for the acceptance of reasonable inference.