Swearing on a Bible is a quite modern concept. A Roman man (women could not go to court except in very special circumstances) placed his right hand on his testicles, while swearing by the gods he believed in, and affirmed he would tell the truth; hence the term 'testimony'.
The left hand is placed on the Bible and the right hand is raised.
Tom Robinson places his hand on the Bible and takes an oath to tell the truth before testifying in court.
The bailiff swears in the witness during a trial. The witness holds their right hand on the Bible and their left hand is in the air.
When taking an oath in court on the Bible, the right hand is traditionally placed on the Bible.
The right hand typically goes on the Bible when taking an oath in court.
Typically, you place your right hand on the Bible when taking an oath in court.
Many Christians, including ministers, believe that the Bible teaches that we should not swear at all, on the Bible or otherwise. So they will usually just say they "affirm" that they will tell the truth.
Traditionally, it was your right hand for cultural reasons. I do not believe that Bibles are used for this purpose any more. I personally appeared as a witness twice (in NY) and both times I was asked to swear to tell the truth. No Bible was presented and I was not asked to raise my hand.
Yes, a person can refuse to swear on the Bible in court. The person should notify the Court in advance since it's a change of procedure. The Court will then have the person simply raise their right hand and swear to tell the truth. Most courts in the United States no longer use a Bible during swear-in of a witness, citing separation of Church and State in due process.
Since oaths are sworn with the raised right hand, the left hand is the only one left to place on the Bible, thus swearing or affirming on the Bible. I think it is not so much significance of the left hand, but that the right hand is always raised for the oath - so the left is the only one left!
The oath is "I swear to tell the truth, the whole truth, and nothing but the truth." As you right hand is held up