The answer of one witness shall not be heard at all; the testimony of a single witness shall not be admitted under any circumstances (for civil cases).

Explanation

(English-origin maxim.) In civil cases, the testimony of a single uncorroborated witness was historically insufficient to establish a fact; this rule enforces the principle that important matters require more than one source of proof.

Where this applies

• A plaintiff's entire case rests on the testimony of one friend who says he saw the accident, but no other witness or physical evidence supports the story — historically, that single uncorroborated account was insufficient.
• A party to a contract dispute calls only one witness to prove the contract existed, while the other side produces documents and multiple witnesses — the single-witness testimony standing alone may not carry the day.
• A will contest turns on whether the testator was mentally competent, and only one person testifies she was — without corroboration, that lone voice may not be enough to establish the fact.