When, however, there is no ambiguity of grammatical construction, but the words themselves require definition, recourse is properly had to extrinsic evidence. Here it is necessary to learn from extrinsic sources the meaning usually attached to these words at the time the Constitution was framed and, presumably, by those who framed and adopted the Constitution. Examples of such technical terms are "letters of marque and reprisal," "ex post facto," "bill of attainder," "bankruptcy," "admiralty," "equity," "direct tax," "duties," "imposts," "excises," "piracy," "habeas corpus," "citizen," "alliance," "confederation," "republican form of government," "infamous crime," "commerce," etc. The technical term "treason" is defined in the Constitution itself.
One of the principal questions involved in the Dred Scott case was as to the definition of the term "citizens of different States" as employed in Article III of the Constitution. The Insular Cases in considerable measure turned upon the meaning to be ascribed to the expression "United States." In Texas v. White it was necessary to enter into a careful definition of the terms "state " and "government" in order clearly to distinguish them.
As has been repeatedly declared by the courts the best rule for interpreting the technical terms employed in the Constitution is to give to them the meaning which they had at the time that instrument was framed and adopted. When the terms are technical law terms they are to be given the meaning attached to them in the English common law.25
25 The Supreme Court in South Carolina v. United States (199 U. S. 437; 26 Sup. Ct. Rep. 110; 50 L. ed. 261) states this doctrine as follows: "It must also be remembered that the framers of the Constitution were not mere visionaries, toying with speculations or theories, but practical men dealing with the facts of political life as they understood them: putting into form the government they were creating and prescribing, in language clear and intelligible, the powers that government was to take. Mr. Chief Justice Marshall, in Gibbons v. Ogden (9 Wheat. 1, 188: 6 L. ed. 23) well declared: 'As men whose intentions require no concealment generally employ the words which most directly and aptly express the ideas they intend to convey, the enlightened patriots who framed our Constitution, and the people who adopted it, must be understood to have employed words in their natural sense, and to have intended what they have said.' One other fact must be borne in mind, and that is, in interpreting the Constitution we must have recourse to the common law. As said by Mr. Justice Matthews in Smith v. Alabama (124 U, S. 465: 8 Sup. Ct. Rep. 564: 31 L. ed. 508): 'The interpretation of the Constitution of the United States is necessarily influenced by the fact that its provisions are framed in the language of the English common law, and are to be read in the light of its history.' And by Mr. Justice Gray in United States v. Wong Kim Ark (169 U. S. 649: 18 Sup. Ct. Rep. 456; 42 L. ed. 890): 'In this, as in other respects, it must be interpreted in the light of the common law, the principles and history of which were familiarly known to the framers of the Constitution. Minor v. Happersett (21 Wall 162: 22 L. ed. 627); Ex parte Wilson (114 U. S. 417; 5 Sup. Ct. Rep. 935; 29 L. ed. 89); Boyd v. United States (116 U. S. 616; 6 Sup. ( Ct. Rep. 524; 29 L. ed. 746): Smith v. Alabama (124 U. S. 465; 8 Sup. Ct. Rep. 564: 31 L. ed. 508). The language of the Constitution, as has been well said, could not be understood without reference to the common law. 1 Kent. Com. 336; Bradley. J., in Moore v. United States (91 U. S. 270; 23 L. ed. 346).' To determine the extent of the grants of power, we must, therefore, place ourselves in the position of the men who framed and adopted the Constitution, and inquire what they must have understood to be the meaning and scope of those grants."
In a few instances it is, however, to be observed, that the Supreme Court has refused to give to technical terms the meanings attached to them in 1789 by the common law. This has been so especially with reference to the words "admiralty" and "bankruptcy" both of which terms have been given a broader meaning' than that furnished by the English common law. Commenting upon this Pomeroy properly says: "The true rule would seem to be this: Where words having a well known, technical sense by the English law are used in the Constitution, and these words are keys to the clauses which protect the private rights and liberties of the people, and especially of clauses which impose direct restraints upon the government in respect of such rights and liberties, and the technical sense itself is necessary for the complete protection of the individual citizen, this signification must still be retained in any interpretation of these provisions. But on the other hand, where words which had a technical meaning by the English law, are used in clauses which relate to the general functions of legislation and administration, and to the .political organization and powers of the government, such sense must be attributed to them as will best carry out the design of the whole organic law, whether that signification be broader or narrower than the one which had received the sanction of the English Parliament and courts."26