Legal Definitions - unus nullus rule

The unus nullus rule is a principle found in some civil law legal systems. It literally translates from Latin as "one is nobody" or "one is no one." This rule dictates that the testimony of a single witness, standing alone, is considered insufficient to establish a fact in court. For a fact to be proven, there must be corroborating evidence or additional witness testimony; the uncorroborated statement of just one person is given no evidentiary weight.

• Contract Dispute: Imagine a small business owner, Ms. Chen, claims that a supplier verbally agreed to a significant discount on a large order. When the supplier sends the full-price invoice, Ms. Chen sues for breach of contract, testifying in court that the agreement was made. However, there were no other witnesses present during the conversation, no emails, no written notes, and no other evidence to support her claim. Under the unus nullus rule, Ms. Chen's sole testimony, without any corroboration, would likely be given no weight by the court, making it difficult for her to prove the existence of the discount agreement.

• Property Boundary Dispute: Consider a dispute between two neighbors, Mr. Davies and Ms. Miller, over the exact location of their shared property line. Mr. Davies testifies that Ms. Miller's new fence encroaches onto his land by several feet, based solely on his personal observation from his backyard. Ms. Miller, however, presents a recent land survey showing the fence is correctly placed. If Mr. Davies's claim relies exclusively on his own testimony without any supporting evidence like a survey, photographs, or another witness, the unus nullus rule would mean his uncorroborated statement alone would not be enough to prove the encroachment against the survey evidence.

• Allegation of Professional Misconduct: Suppose a client, Mr. Evans, files a complaint against his financial advisor, alleging that the advisor provided misleading information during a private meeting, leading to significant financial losses. Mr. Evans testifies to the advisor's specific misrepresentations. The financial advisor denies the allegations, and there were no other individuals present during the meeting, nor any written communications or recordings of the alleged misleading advice. In a jurisdiction applying the unus nullus rule, Mr. Evans's testimony alone, without any other evidence to support his claim, might be deemed insufficient to prove the professional misconduct against the advisor's denial.