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 New Jersey, evidence is regulated by both state statutes and rules of court, particularly the New Jersey Rules of Evidence. These rules determine what evidence is admissible in court. Evidence must be relevant, meaning it must have any tendency to make a fact more or less probable than it would be without the evidence and the fact must be of consequence in determining the action. Physical evidence, digital records, and witness testimony are all subject to these rules. Expert witness testimony is also admissible, but it must meet certain standards of reliability. The judge acts as the gatekeeper in determining the admissibility of expert testimony, ensuring that it is based on sufficient facts or data, is the product of reliable principles and methods, and that the expert has applied the principles and methods reliably to the facts of the case. The reliability standard for expert testimony in New Jersey follows the guidelines set forth in the landmark federal case Daubert v. Merrell Dow Pharmaceuticals, Inc., which has been adopted by New Jersey courts.