Evidence is information that exists in physical or digital form—such as written agreements and e-mail communications—as well as testimony from witnesses who have personal knowledge of facts relevant to a dispute. Evidence generally must be relevant to be admitted in court and considered by the factfinder (judge or jury) in resolving a lawsuit. And some forms of evidence, such as expert witness testimony, must be shown to be sufficiently reliable (as determined by the judge) to be admitted in evidence.

In West Virginia, as in other jurisdictions, evidence must be relevant and reliable to be admissible in court. Relevance means that the evidence must have a direct bearing on the case at hand, helping to prove or disprove a material fact in dispute. Reliability pertains to the quality of the evidence, ensuring that it is trustworthy and credible. Physical evidence, such as written agreements, and digital evidence, like email communications, must be authenticated to be admitted. This involves demonstrating that the evidence is what it purports to be. Testimony from witnesses, including expert witnesses, is subject to rules that assess the witnesses' personal knowledge of the facts and the reliability of their testimony. Expert witness testimony, in particular, must meet specific criteria for scientific, technical, or other specialized knowledge, and the judge acts as a gatekeeper to determine whether the expert's methods are sufficiently reliable and relevant to the case. These rules are guided by the West Virginia Rules of Evidence, which align with the Federal Rules of Evidence in many respects.