One of the very oldest principles of our legal heritage is that the king is subject to the law. King John was taught this principle at Runnymede in A.D. 1215, when his barons forced him to submit to Magna Carta, the great charter that imposed limits on the exercise of sovereign power. In a government of laws, existence of the government will be imperilled if it fails to observe the law scrupulously. Our Government is the potent, omnipresent teacher. For good or for ill, it teaches the whole people by its example.
Crime is contagious.
Against that pernicious doctrine this Court should resolutely set its face. This venerable principle will not give way to the expediency of the government's present practices without legislative authorization. The public policy against payments to fact witnesses is expressed in the majority of states in both the law of contracts and in ethical rules, which we address below. The judicial process is tainted and justice cheapened when factual testimony is purchased, whether with leniency or money. The government asserts, without argument or authority, that agreements for testimony between the government and a witness are not contemplated by this statute.