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 Georgia, evidence is regulated by the Georgia Evidence Code, which aligns with the Federal Rules of Evidence in many respects. Evidence must be relevant to the issues in a legal dispute to be admissible in court. Relevance is determined by whether the evidence makes a fact more or less probable than it would be without the evidence, and whether that fact is of consequence in determining the action. Physical and digital evidence, such as written agreements and email communications, must be authenticated to be admitted. This means that the party offering the evidence must present sufficient proof that the evidence is what it claims to be. Testimony from witnesses with personal knowledge of relevant facts can also be admitted, provided it complies with the rules of evidence, including those against hearsay, unless an exception applies. Expert witness testimony must meet additional reliability standards; the expert's opinion must be based on sufficient facts or data and be the product of reliable principles and methods that the expert has applied reliably to the facts of the case. The judge acts as the gatekeeper in determining the admissibility of evidence, including the reliability of expert testimony.