The speeches of Cicero provide a rich field of study for legal historians and historically interested jurists in many ways. They offer a detailed picture of the court system and the rules of evidence during the late Roman Republic. This work focuses on witness testimony and explores it comprehensively. Based on this, and in comparison with other authors from different periods, it addresses important questions regarding the procedure, the personal qualifications of the witness, the credibility of the testimony, and offenses related to witness testimony. The findings of this work shed new light on the various aspects of witness testimony during the late Roman Republic and allow for a deeper understanding of today's rules of evidence in their historically evolved context.