Things That Make You Go, "Hmmm": If church and state are supposed to be separate in the United States, why do we swear on bibles in courts?

The following is from the book Life's Imponderables™, by David Feldman, ©1969, pages 301-303

The ritual of taking an oath with the right hand raised while placing the left hand on a holy object goes back to ancient times.  Michael De L. Landon, secretary of the American Society for Legal History, has pictorial evidence of the Bayeux Tapestry, which depicts King Harold of England, who reigned from 1035-1040, taking an oath with both hands on a sacred object.
In the Middles Ages, before printed Bibles were commonly available, Christians placed the left hand on a relic of a saint or some other sacred object and raised the right hand while taking an oath.  Professor De L. Landon comments:

The right hand raised and open, palm outward, is an internationally recognized gesture implying peace, honesty, and good intentions.  In taking an oath, there is also probably the indication that one is pointing to heaven and calling upon God (or the gods) to be one's witness that one is sincere and telling the truth.

The English adopted the practice of having witnesses swear an oath on the Bible before testifying.  American law was based originally on an English common law that stipulated that only witnesses who believed in a Supreme Being could testify at a trial.  The framers of the common law assumed that only the fear of an eternal punishment would ensure the honesty of the witness.  Lord Coke, the leading English jurist of the early seventeenth century, went further and argued that nonconformists as well as atheists were petui inimici ("eternal enemies") and should be barred from testifying.  Coke's position was adopted by the English for almost two hundred years, and although it became impossible to enforce the doctrine, Parliament did not actually remove the statute until 1869.

Most courtrooms have stopped using Bibles to swear in witnesses, for the ritual was always a ceremonial demonstration of good faith rather than a legally mandated procedure.  Most courts traditionally have used King James Bibles, but have allowed Jews or Catholics to substitute versions that were acceptable to their faith.

The United States adopted the rule disqualifying disbelievers in the Federal Judiciary Act of 1789, which provided that no one could testify "who did not believe that there is a God who rewards truth and avenges falsehood."  In 1906 Congress passed an amendment to allow states to determine their own rules for their own courts, although most states had already passed statutes voiding the disbeliever clause.  Even today, a few states have not struck down the disbeliever clause; theoretically, an atheist could be barred from testifying in a trial in those states.

In his book, Church, State and Freedom, Leo Pfeffer notes broader constitutional provisions ensure that no civil rights may be denied because of religious beliefs.  Still, the issue hasn't been addressed squarely by the Supreme Court, and Pfeffer documents a scary application of how the nonbeliever clause has been applied in the past:

In 1900 the Court upheld a Federal statute that required that the testimony of Chinese, in certain cases, be corroborated by that of white men, because of the loose notions entertained by (Chinese) witnesses of their obligation of an oath.'  It would seem clear that if a defendant in a criminal case or a party in a civil case could not take the stand in his own behalf because of his religious beliefs or disbeliefs, he would be deprived of his liberty or property without due process of law and would be denied the equal protection of the laws in violation of the Fourteenth Amendment.  Moreover...the 'free exercise' clause of the First Amendment protects religious disbelief as well as belief....

As might be expected, both the ACLU and Madalyn Murray-O'Hair's Society of Separationists have been in the forefront of litigation attempting to eliminate swearing on Bibles (as well as elimination other elements of religion in the courts).  The path of least resistance, for most jurisdictions, has been to abandon the use of Bibles.

One need not be philosophically opposed to the use of Bibles in the courtroom to note that a Bible has never been a guarantee of truthful testimony; perjurers have been swearing on Bibles for a long, long time.