Legal Definitions - quantitative rule

A quantitative rule in law is a principle of evidence that dictates certain types of evidence, by themselves, are not strong enough to prove a fact or win a case. To be considered sufficient, this specific type of evidence must be supported or corroborated by additional, independent evidence before the legal proceedings conclude. These rules are put in place because legal systems recognize that some forms of evidence carry inherent risks of unreliability, misunderstanding, or potential fabrication, and therefore require extra safeguards to ensure fairness and accuracy in legal proceedings.

• Example 1: Proving a Will

  Imagine a situation where a person has passed away, and their last will and testament needs to be legally validated in court. Many jurisdictions have a quantitative rule requiring that a will must be attested to by at least two witnesses who were present and saw the testator (the person making the will) sign it. The testimony of just one witness, even if truthful, might not be enough to legally prove the will's validity. This rule exists to prevent fraud or disputes, as relying on a single person's account could be more susceptible to error or fabrication.

• Example 2: Conviction for Perjury

  Consider a prosecutor attempting to convict an individual for perjury, which is the crime of lying under oath in court. In many legal systems, a conviction for perjury cannot rest solely on the testimony of a single witness who claims the defendant lied. The law recognizes the ease with which one person could falsely accuse another of lying. Therefore, a quantitative rule demands additional corroborating evidence—such as documents, recordings, or the testimony of a second witness—to support the claim of perjury and ensure a more reliable conviction.

• Example 3: Historical Treason Laws

  Historically, and enshrined in some modern constitutions (like the U.S. Constitution, Article III, Section 3), laws concerning treason against the state often included a quantitative rule. For instance, to convict someone of treason, it might have required the testimony of at least two witnesses to the same overt act of treason. Treason is a crime with extremely severe penalties, often politically charged. To prevent false accusations and ensure a very high standard of proof, this rule mandated multiple witnesses to the same specific act to corroborate the accusation, rather than relying on a single account which could be biased or mistaken.