Rule 603 Oath or affirmation.

Before a witness can testify in court, they must first promise to tell the truth. This promise can be made through a traditional oath or through an affirmation, and the person can choose either option.

The key point is that the promise has to feel real and meaningful to the person making it. The words used should remind the witness that they have a serious duty to be honest, and the format should be one that speaks to their own sense of right and wrong. This means courts have some flexibility in how they administer the oath, as long as it does what it's supposed to do: make the witness understand they must tell the truth.

This rule protects the fairness of trials. When witnesses understand they are bound by a real promise to be truthful, it helps make sure the information the court hears is honest and reliable.