From the early episodes of the “Perry Mason” television series to the courtrooms at the Thomas Eagleton Federal Courthouse in downtown St. Louis, this familiar oath is required before a witness can testify at trial.

The use of these 10 words in 2012 follows a historical path that dates back to the land of Athens — ancient Greece. That’s where the Greek scholar Origen first uttered his famous observation:  “Conscience is the chamber of justice.”

Conscience? Oath? Truth? What do all these have in common?

According to a decision of the Missouri Supreme Court in 1890, the purpose of an oath, regarded as a feature of judicial procedure, is its “quickening of the conscience.” State v. Bennett, 14 S.W. 865 (Mo. 1890).

However, between the days of the toga and creation of the Lake of the Ozarks, the concept of oath and conscience underwent some development. Around 930 A.D., the Anglo-Saxon king Athelstan codified Britain’s laws, and included a section requiring that the sale of chattel be witnessed by a neutral third party, who would take an oath to act truthfully and in the law’s best interest.

More tweaking occurred in the 13th century, which marked the first use of the phrase “the truth, the whole truth, and nothing but the truth,” which became a staple of English trials in that era.

The oath tradition later carried over to America. Noah Webster, for example, refers to the “whole truth” oath in a 1787 essay. The 1856 edition of Bouvier’s Law Dictionary notes that, after swearing the oath, witnesses were expected to kiss the Bible.

Back to the Show Me State, the Missouri Legislature adopted a similar tone in its 1886 statute which deemed that a person would be lawfully sworn in by swearing, affirming or declaring, in whatever form, “in the same manner as if he had sworn by laying his hand on the gospels and kissing them.” V.A.M.S. 492.060.

Thus, a vital part of our litigation system is designed around the conscience — something invisible, intuitive and hard to describe. Commonly used metaphors for conscience include the “voice within” and the “inner light.” The famous Missourian Mark Twain put his own spin on the concept when he noted, “Good friends, good books and a sleepy conscience: this is the ideal life.”

Mr. Twain would not likely have been the first in line for a circuit judge opening in Marion County Circuit Court!

A more moderate viewpoint comes from the journalist/satirist H.L. Mencken, who observed, “Conscience is the inner voice which warns us that someone may be looking.”

As lawyers, we are also obligated to be sworn in as members of the Missouri Bar by taking the oath of admission. We do solemnly swear that we will support the Constitution of the United States and the Constitution of the State of Missouri, and will at all times conduct ourselves with dignity becoming of an officer of the court in which we appear.

If there ever comes a time when you are holding up your right hand and preparing to quicken the conscience, rest assured that one of our attorneys will be nearby as your zealous advocate.

We take very seriously all oaths and affirmations. We pledge to our existing and new clients that at all times we will conduct ourselves to the best of our knowledge and ability, with respect due the courts of justice.

And that’s the truth.