If a person testifying in court is a known atheist, are they still required to swear on the bible? And if so, I guess the court is relying on that atheist's morals alone to pull through and tell the truth, right?
1) The oath/affirmation is a traditional declaration that expresses the witness’ assurance that the testimony given will be the truth and nothing but the truth.
2) Not all courts use the bible. Some don’t use it at all. Others only require raising the right hand. Laying one’s hand on a bible or a saying “so help me god” are just historical appendages to the main point which is telling the truth. I have no issue with taking an oath as is. They remind me of the following anecdote:
At a lunch party I was placed next to a well-known female rabbi, now ennobled. She asked me, somewhat belligerently, whether I said grace when it was my turn to do so at High Table dinner in my Oxford college. “Yes,” I replied, “Out of simple good manners and respect for the medieval traditions of my college.” She attacked me for hypocrisy, and was not amused when I quoted the great philosopher A J (Freddy) Ayer, who also was quite happy to recite the grace at the same college when he chanced to be Senior Fellow: “I will not utter falsehoods”, said Freddy genially, “But I have no objection to making meaningless statements.”
3) The court relies on facts. That is why there is such a thing as perjury if a testimony is shown to be false.
Thanks for the question. Hope it helps.