Witness testimony has long been regarded as one of the most significant forms of evidence in criminal proceedings. However, in the context of international crimes, due to their scale and complexity, the role of witness testimony extends beyond criminal courts. It has also become a crucial tool in truth commissions, which aim to promote transitional justice and restore public trust. These commissions, established to document widespread violations of human rights and international humanitarian law, place truth-seeking at the core of their mission. The key question is to what extent the findings of these quasi-judicial bodies can be relied upon in criminal courts and whether they possess evidentiary value in international criminal proceedings. Using a descriptive-analytical approach, this study first examines the foundations and functions of truth-seeking in truth commissions and then, through a comparative analysis of the Sierra Leone Truth and Reconciliation Commission and the Special Court for Sierra Leone, evaluates the credibility and admissibility of the evidence and testimonies produced in these processes. The findings show that although the evidence and testimonies collected by truth commissions can play an effective role during the investigative stage, particularly in supplementing evidence and reconstructing the historical reality, they possess limited evidentiary value in criminal proceedings due to shortcomings such as the absence of cross-examination, the lack of verification and assessment of the accuracy of testimonies, and the commissions’ substantive involvement in issues of criminal liability beyond their mandate.