A corroborating witness is a witness whose evidence supports, confirms or strengthens the testimony of another witness or the overall case theory, making that evidence more reliable and persuasive. In practice, corroboration may come from eyewitness accounts, documents, expert evidence, CCTV or other independent sources.Across England & Wales, Scotland, Northern Ireland and Ireland, the term is descriptive rather than usually defined in statute. However, corroboration has particular historical significance in Scots law, where certain types of proof traditionally required evidence from at least two independent sources. Some sexual offence and vulnerable witness contexts across the jurisdictions also feature specific rules or guidance on when corroborative evidence is needed or desirable.In both criminal and civil proceedings, corroborating witnesses are important for assessing credibility, resolving conflicts of evidence and meeting evidential thresholds such as “beyond reasonable doubt” or “on the balance of probabilities”. Courts scrutinise whether corroborating witnesses are truly independent, consistent and free from collusion. While corroboration is not always legally required, the presence or absence of a corroborating witness can be critical in trial strategy, case assessment and appellate review.