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 North Dakota, evidence is regulated by both state statutes and rules of court, particularly the North Dakota Rules of Evidence. These rules dictate that evidence must be relevant to the facts of the case 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 if that fact is of consequence in determining the action. Physical and digital evidence, such as written agreements and email communications, must adhere to these standards of relevance. Additionally, witness testimony is considered evidence if the witness has personal knowledge of the facts relevant to the dispute. Expert witness testimony is subject to a reliability standard, which is assessed by the judge. The expert's methodology and the relevance of their testimony to the issues at hand must be established before their evidence is admitted. The North Dakota Rules of Evidence are designed to ensure that the evidence presented in court is both reliable and pertinent to the resolution of the case.