These rules govern proceedings in the courts of the United States and before the United States bankruptcy judges and United States magistrate judges, to the extent and with the exceptions stated in rule 1101.

These rules shall be construed to secure fairness in administration, elimination of unjustifiable expense and delay, and promotion of growth and development of the law of evidence to the end that the truth may be ascertained and proceedings justly determined.

When evidence which is admissible as to one party or for one purpose but not admissible as to another party or for another purpose is admitted, the court, upon request, shall restrict the evidence to its proper scope and instruct the jury accordingly.

Before testifying, every witness shall be required to declare that the witness will testify truthfully, by oath or affirmation administered in a form calculated to awaken the witness’ conscience and impress the witness’ mind with the duty to do so.