The catchall term "secondary sources" encompasses a wide variety of publications. The characteristic all of these publications share is that they consist of descriptions of or commentary on the law, and not the law itself. The law upon which your analysis of a problem must ultimately rely is embodied in primary authorities (constitutions, statutes, case law and regulatory materials) which may be mandatory or persuasive depending upon the controlling jurisdiction. Secondary authorities can serve many purposes, but can never be mandatory or binding precedent. Keep in mind when using these sources that they must never be used as the essential underpinnings of your legal analysis or argument.
Nevertheless, secondary sources can be invaluable aids to the researcher. They may be profitably consulted at almost any stage of the research process.
Secondary sources can provide a springboard for beginning a research project. At this stage the researcher may consult secondary sources:
to obtain background information and an overview of an unfamiliar or emerging area of law;
to obtain citations to primary authorities to launch the research;
to suggest further issues or analytic approaches to the problem.
Secondary sources can also be valuable midway through or closer to the end of a research project, when consulting them can help to confirm conclusions or refine analysis.
Obviously, for any particular research project, you do not need to consult all the secondary sources available. This contrasts with the importance of comprehensiveness in primary authority research. Eventually you will develop preferences among the sources available, along with an instinctive sense for which sources might be helpful for a given project. Additionally, the resources available at the location where you are conducting your research will dictate some of your choices. The following are some guidelines for choosing a secondary source for a particular topic and for using secondary sources in general:
If you are researching a topic which is completely unfamiliar to you, some background reading may provide an overview of the basic structure and sources of law on the topic. A treatise may be helpful at this stage if it is not overly detailed. Sometimes a hornbook or even a Nutshell can provide the quick introduction to a topic area and the ideas for research vocabulary which a beginning researcher needs.
Highly scholarly law reviews, treatises, and the Restatements are probably not good starting places for most research projects unless you already know a great deal about the subject area.
Usually in the early stages of researching a state topic you will be focusing on the primary authorities from the controlling jurisdiction. If you need to expand your research to seek persuasive authority from other jurisdictions, consulting a secondary source such as American Law Reports (A.L.R.) or one of the national law encyclopedias may help.
Generally, when consulting secondary sources, choose the most up-to-date available. The sources which can provide the most current references to primary sources will probably be the most useful.
Make certain to focus on the primary sources cited in the secondary sources you use, rather than spending precious research time trying to thoroughly digest the content of each secondary source. Do not accept the theory of the source's author uncritically - your own reading of the primary authorities may lead you to different conclusions.