What must a lawyer not knowingly do to a tribunal?

A lawyer must not knowingly make a false statement of fact or law to a tribunal because this violation undermines the integrity of the judicial system. The role of a lawyer is to uphold the truth and advocate for their client while ensuring that the legal process is conducted in a fair and just manner. Making false statements can lead to serious consequences, including the potential for sanctions against the lawyer, damage to their reputation, and the distortion of the truth in legal proceedings. This obligation reflects the broader ethical standards required by the legal profession to ensure that justice is served and that the tribunal can rely on the information presented to it.

The other choices, while also related to ethical obligations, do not specifically highlight the critical nature of truthfulness to a tribunal. Failing to present all evidence available could hinder a lawyer's effectiveness but does not inherently involve knowingly deceiving the court. Communicating secretly with opposing counsel presents risks but is not directly related to the obligation to be truthful to a tribunal. Disclosing client information without permission relates to confidentiality issues, which are also crucial, but it doesn't address the duty of truthful representation before the court. The paramount significance of honesty in legal proceedings makes the first choice the most pertinent in this context.