דברים, פרק י״ט, פסוק כ׳

A functional justice system relies on the absolute truth of those who come forward to testify. When individuals scheme to deliver false testimony, their severe punishment serves as a powerful tool for broad public deterrence. Knowing the heavy price exacted for attempting to falsely harm another person instills a deep sense of awe, teaching society that giving evidence must be approached with extreme caution, accuracy, and gravity [ביאור שטיינזלץ].

To achieve this deterrence, the court is obligated to make a formal, public announcement detailing the identities of the false witnesses and the penalties they face [רש״י, תורה תמימה, אדרת אליהו]. Interestingly, this requirement for a public declaration is exceptional. It is one of only four specific instances in biblical law demanding such publicity, reflecting the uniquely destructive nature of these crimes. This rarity demonstrates that public deterrence is not the underlying purpose of all punishments, but a measure reserved for distinct, highly damaging offenses [רש ר הירש].

The warning generated by this punishment is not directed at the entire nation indiscriminately. Since certain individuals, such as thieves, are already legally disqualified from testifying, the warning specifically targets only the remaining public—those who are legally fit to serve as witnesses [שפתי חכמים, רש ר הירש]. Furthermore, the execution of this deterrence is immediate and local. While other severe crimes might see punishments delayed until a pilgrimage festival in Jerusalem to ensure maximum exposure, plotting witnesses are judged and publicly exposed right away in their local court, without waiting for a holiday [גור אריה].

The stringent rules governing false testimony apply across the board, covering both capital and monetary cases [אדרת אליהו], though there is an opinion that monetary cases might not strictly require a public announcement [העמק דבר]. Crucially, these laws only take effect if the false statements are delivered formally within a court of law; claims made outside of an official legal setting do not carry the same penalty. The consequences also extend to anyone who joins the conspiracy later. Even if a large group of witnesses subsequently aligns with a false testimony already presented in court, and the entire group is later exposed as fraudulent, every single participant receives an equal punishment [אדרת אליהו].

The ultimate goal is that such corrupt acts will never be repeated. While this is generally understood simply as the natural result of successful deterrence, some commentators view this expectation as the formal biblical prohibition against plotting as a false witness. Conversely, others maintain that the formal prohibition is not derived from this context at all, but rather originates directly from the Ten Commandments, which explicitly forbid bearing false witness against a neighbor [בכור שור].