• Sources are only persuasive when they are not binding and cannot influence a court directly.
• All secondary sources and primary sources from another jurisdiction are persuasive.

In legal research, secondary sources are concepts with multiple meanings, but their main role is well-settled. Secondary sources help the researcher find the answer, the primary sources. How that role is performed depends on many factors, and most importantly perhaps, their meaning.

Within their broader sense, secondary sources have a more complex supporting role. They
• identify relevant legal scholarship (indexes)
• identify legal meanings for polysemic concepts (dictionaries), and
• identify the correct repositories of law (research guides).

In their narrower meaning secondary sources represent narratives which explain the meaning of primary sources, of the law. As such, secondary sources have a somewhat lesser role in American law, than the pervasive role the doctrine, “la doctrine” or “la dottrina” has in both international law and in civil law systems. The doctrine is the product of writings of professors and other scholars, which both explains and evidences the law. In American law, they only persuade judges to accept a certain interpretation of a statute, or certain case as the precedent to be followed.

Among secondary sources, as further defined here, legal scholarship, the American version of legal doctrine, has a more nuanced role, which stems from that initial plan of action all researchers encounter, whether they are aware of it or not.

American sources of legal scholarship
• explain the research question;
• explain research options;
• focus the researcher’s attention to a specific legal area, and
• identify potentially relevant primary sources.

Typically, secondary sources are useful because they function as a finding-aid tool. They help locate relevant legal scholarship (indexes) or even relevant primary sources (legal scholarship). For a student of law, because they summarize, restate, review, analyze, and interpret the law, secondary sources, especially legal scholarship, may often represent both the beginning and the end of the legal research process.
For example, if you write a paper about the New York law regarding non-criminal “unconscious aiding and abetting,” reading some piece of legal scholarship may be all you need to do. There are many strategies to find what you need in the most effective way. If you deem that the issue is esoteric enough, then rather than consulting a book, an article, such as a law review article, may be the fastest way to find what you need. Once you identify the best index to locate relevant law review articles, you use it to perform a search for articles. In this instance, you may find that a law article, such as the one identified as 16 TOURO L. REV. 25 (1999), offers you the information you need.
Legal practitioners look at a secondary source in a different way than a non-practitioner. Secondary sources help them start the legal research process, and may help them frame a legal argument when they present their client’s case in front of a judge. When practitioners cannot find a binding primary source, then they look for sources of persuasive authority. Thus, for practitioners, whether attorneys, or law librarians, secondary sources rarely represent the end of the legal research process. By their very essence, they are a commentary on specific legal rules, and not the law itself.