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 Hampshire, evidence is crucial in legal proceedings and must adhere to rules that ensure fairness and reliability. Evidence can be in the form of physical documents, digital records, or witness testimony. For evidence to be admissible in court, it must be relevant to the case, meaning it should have a direct bearing on the dispute at hand. The relevance of evidence is determined by whether it makes a fact more or less probable than it would be without the evidence. Additionally, certain types of evidence, such as expert witness testimony, are subject to further scrutiny. Expert testimony must be evaluated by the judge for reliability before it can be presented to the factfinder (judge or jury). The judge will consider factors such as the methodology used by the expert and whether their findings can be tested and have been subject to peer review. New Hampshire follows the Federal Rules of Evidence as a guideline, but also has its own set of rules codified in the New Hampshire Rules of Evidence which attorneys must navigate in court proceedings.