Quotable Jefferson (searching in the index under "jury trial," "judgment," "scholars," and "farmers")
Earliest known appearance in print: This quotation has not appeared in print so far as we know.1
Earliest known appearance in print, attributed to Jefferson: This quotation has not appeared in print, although it was attributed to Jefferson by Glenn Beck in a December 18, 2009 appearance on The Jay Leno Show.2
Other attributions: none known
Status: This exact quotation has not been found in any of the writings of Thomas Jefferson. It may be a reference to Jefferson's comment to his nephew Peter Carr, "State a moral case to a ploughman and a professor. The former will decide it as well, and often better than the latter, because he has not been led astray by artificial rules."3
1. To establish the earliest appearance of this phrase in print, the following sources were searched for the phrases "12 scholars" and "12 farmers": Google Books, Google Scholar, Amazon.com, America's Historical Newspapers, American Broadsides and Ephemera Series I, Early American Imprints Series I and II, Eighteenth Century Collections Online, 19th Century U.S. Newspapers, American Periodicals Series Online, JSTOR.
2. LiveDash.com, "The Jay Leno Show," Aired on Friday, Dec. 18, 2009 (12/18/2009) at 11:00 P.M.
3. Jefferson to Carr, August 10, 1787, in PTJ, 12:15. Transcription available at Founders Online.