This post first appeared at lawlibrary.case.edu.
In legal research, when we refer to a “secondary source” we mean a document that is not, itself, legal authority but that explains or describes the law. By contrast, the verbal, documentary, nature of law is such that a “primary source” text—such as a statute or a judicial opinion—is in itself “the law.”
Secondary sources can be valuable tools at any stage in a research process. All of the many genres of secondary sources can be analyzed according to their usefulness at providing:
- Explanation of the law. From a dictionary definition on up to an extensive multi-volume treatise, secondary sources often attempt to define and explain the nature of the law relevant to a queried subject.
- Citations and references. Many of the most valued secondary sources for legal research are richly endowed with careful citation and reference both to the primary sources—the law itself—and to other secondary sources.
- Persuasiveness. Some secondary sources have actual influence upon the development of the law. In conducting basic topical legal research, this is a value to be cautious of: Secondary sources by definition are not the law, and can never substitute for finding and referencing the actual legal authorities. One kind of secondary source, the Restatements of the Law, have a unique kind of “authority” discussed here.
- Contextualization. This last virtue is perhaps the one most easily overlooked, but is an important quality of those secondary sources, such as legal encyclopedias and (especially) treatises, that present an extended and organized overview of a legal topic. Here, the value is not merely “explanatory” in the sense of providing a direct answer to a specific topical query, but deeper in providing an overall placement of the discussion of one specific topical point within someone’s broader analysis of a whole area of the law.
If you are reading this site, you likely have a passing familiarity with some genres of legal secondary sources. You may have turned for research answers to legal encyclopedias like American Jurisprudence, 2nd (Am.Jur.2nd) or Corpus Juris Secundum (C.J.S.). You have probably been shown a legal treatise, or at least the short form known as a hornbook. You’ve doubtless used a law dictionary. And you have almost certainly seen law review articles, or at least extended excerpts from them reprinted in your casebooks.
In a coming series of posts, we’ll discuss various major genres of legal secondary sources in terms of how they stack up against the four values mentioned above.