Raise your right hand...

I’m assuming this is so because the left hand is supposed to be resting on a Bible. But why shouldn’t the right hand rest on the Bible instead, there being more right-handed people than left-handed? Because the heart is on the left side??

And why does the Court clerk have to raise his or her hand as well?

IIRC, an oath has to be administered by a representative of the county where the oath is taken. i witnessed a vehicular homicide once and was given an oath prior to giving a statement by the detective who had the case so i wouldn’t forget any of the details. he was also required to be a notary public, but i don’t know if that had anything to do with it.

First of all, it is a matter of state law as to who the officials are before which an oath or acknowledgement can be taken. For instance, New York Real Property Law sec. 298 identifies the officials who qualify in New York. Judges and court clerks are obviously on the list, but there is also an official known as a notary public, who (at least in the U.S.) is simply an individual who has been granted the power to take oaths and acknowledgements. In many states, attorneys automatically have the powers to take oaths and acknowledgments, but in New York an attorney must get separately qualified as a notary. (Note that in many European and other civil law countries, the role of a notary is very different.)

In any event, I’ve taken countless oaths and acknowledgements as a notary public. There is no requirement that the person swearing raise any hand. Typically, I will just ask the person “do you so swear” after they have signed an affidavit (or “do you so acknowledge” after they have signed a document to be acknowledged).

I believe that the raising of the right hand is merely customary. Obviously, if it were a legal requirement there would be problems with persons with disabilities.

Interesting to learn that, contrary to what we see in news reports and in films, there is no requirement as such. You go on to say

I take it you’re referring principally to witnesses. What I’ve always found a bit odd was the fact that the administering officer (in court at least) also followed the same procedure (i.e. raising of the hand).

Accessorily, how did this practice of raising the hand in this context come about?

I, too, have seen a raised right hand used fairly universally for swearing on oral testimony in court and in depositions, as well as for swearing in of officials (e.g. when I was admitted to the bar). I have no idea of the history of the practice, however.

Mods, if you decide that it’s a separate question, do whatever you want.
**I’m assuming this is so because the left hand is supposed to be resting on a Bible. **
I have another question: we have separation of church and state. Why the Bible in the first place? And ubiquitos “In God we trust”. And the taxpayer paid chaplain in the Congress? Etc. But no (silent or any) prayer in the school?