What are digests?
In the official case reporters, cases are published in the order they are decided (chronological order), not by the subject of the case. This makes it difficult to locate cases relevant to your research. Digests are indexes to case law - they organize cases by topic and make it much easier to find appropriate cases. All state courts and the federal courts have digests devoted to them; for Texas researchers, the most relevant digests are the Texas Digest and the Federal Digest.
How do I use a digest?
Digests are organized alphabetically by topic. The whole digest consists of many individual volumes, and the spine of each volume lists the topics that are included in that volume. These topics are further broken down into key numbers, which narrow the broad topic down to very specific points of law. When you look up a key number, you'll see summaries of all of the cases that deal with the point of law in the jurisdiction that the digest is covering.
A single case may cover many different points of law, so it might be listed under many different key numbers within a topic or even under multiple topics. See the next box for more information about how to use the topic and key number system to find cases.
Are digests online?
Westlaw and Lexis both offer online equivalents of the digests. Westlaw uses the West topic and key number system, and Lexis uses the headnote system. The publisher of many of the digests also owns Westlaw, so its content is identical to the print digests. Lexis uses its own headnote system, which may not match the West system. For more information about these systems, see the box immediately below this one.
When should I use the print digests instead of the online ones?
This is largely a matter of personal preference. Some researchers find it easier to locate relevant topics in print format as opposed to electronic. The main advantage of the online digests is currency - they are always up to date, while the print digests require users to check updating materials.
How can I tell if a print digest is current?
What is a topic?
Topics are general subject headings. Each digest is divided into dozens of topics, organized alphabetically. Every volume of a digest has a table in the very front of the book listing all of the topics, explaining how they're organized and giving the index abbreviations for each topic.
What is a key number?
Topics are general areas of law, but assigning cases just to a topic doesn't help researchers very much - there may be hundreds or thousands of cases on some topics. To narrow down the topics into more specific, useful categories, they're organized into subtopics, and even sub-subtopics. These subtopics are assigned numbers, called key numbers, to help you locate them easily.
Every topic starts with key number 1 and continues from there. This means it's important to have both a topic and a key number - if all you know is that the case you want was assigned "key number 25", there's no way to find it, since every topic will have a key number 25 in it.
As an example of the topic and key number structure, let's take a look at the topic "Bankruptcy". The main topic is divided into 20 subtopics, which are themselves divided into multiple sub-subtopics, each of which encompasses several key numbers. The beginning of the first Bankruptcy subtopic looks like this:
BANKRUPTCY
I. IN GENERAL, 
2001-2120
2001-2010
2001 In general 2002 Application of state or federal law in general 2011-2040
2011 In general 2012 Bankruptcy power generally 2013 Validity of bankruptcy laws 2021 Construction and operation 2023 Retrospective operation 2024 Validity of retrospective operation 2026 Repeal
You can see that this is organized like an outline, starting from the general and narrowing down by steps until you get to very specific topics. If you understand this structure, it'll help you understand how to effectively search the digests, either online or in print.
What if I don't know my topic or key number? How can I find cases on the subject I'm interested in?
Locating topics in print digests:
If you don't have a specific topic or key number, but know the subject you want to look up, you can use the general index for the digest to locate relevant topics and key numbers. The index is at the end of the digest set. A good way to begin is to search for specific terms, then move to more general terms if you're not finding what you need.
Locating topics in online digests:
To search topics and key numbers on Westlaw, log on to Westlaw (a Westlaw subscription is required) and click on the "Key Numbers" link on the main page. This will take you to the main topic and key number page, where you can either browse through the topics or search the entire topic and key number database for keywords.
To search headnotes on Lexis, log on to Lexis (a subscription is required), click the Browse menu at the top left of the screen, and either browse or search the Topics index. Selecting a headnote topic will simply give you all of the cases that are assigned to it, although Lexis offers many other options for narrowing down the list of results. Also note that the topics and key numbers you would use in Westlaw or in print digests do not correspond to Lexis headnotes.
What if I have a case and want to find other cases on the same topic?
If you have a copy of the case from any of the National Reporter System reporters, it will already have topics and key numbers assigned to it and printed at the beginning of the case. You can simply look these up in print digests or in Westlaw. You can also look up the case on Westlaw or Lexis, see what key numbers or headnotes have been assigned, and click on the ones you're interested in to be taken to a list of other cases that have been assigned the same key number or headnote.
If you only have a citation, or you don't have a copy of the case with the topic and key number information already present, you have a couple of options. You can, as stated above, look up the case on Westlaw or Lexis and proceed from there. If you prefer to use print digests, you can use the Table of Cases (a several-volume set located at the end of the digest, near the General Index) to look up the case and see what topics and key numbers it's been assigned. You can then look up those references in the appropriate digest volumes.
When researching case law, it's vital to find out whether a case you're thinking of citing is still good law. If the case has been criticized by courts in your jurisdiction, or worse, if it's been overturned or superseded, you need to know about it. The way to find this information is to use a citator - a service that tells you exactly what other courts have said about a case.
Using citators online:
With the advent of electronic legal research, citators have largely moved online, where they're much easier to use and can be updated almost instantly. If you have access to Westlaw or Lexis, it's strongly recommended that you use them to check the history of a case. Which service to use is largely a matter of preference; each will present the same basic information about the case's history, but the details - such as whether the citation report lists law reviews that cite the case - may differ.
Westlaw's citator service is called Keycite. To use it, log on to Westlaw (subscription required) and look up the case. Westlaw uses flag icons to indicate whether a case has any negative history - if you see a red or yellow flag in front of the case name, click on it to go directly to the case's "Negative Treatment" tab. If there is no negative treatment, click on the "History" tab near the top of the page. This will show you any direct history of the case, including whether it was appealed and what happened on appeal. Finally, click on the "Citing References" tab. This will show you a list of all cases and other sources that have discussed this case in some substantial way, how much they discussed it, and the nature of the analysis.
Lexis Advance's citator service is called Shepards. To use it, log on to Lexis (subscription required) and look up the case. Like Westlaw, Lexis Advance uses icons to indicate potential negative treatment, so if you see a red or yellow triangle icon in front of the case name, click on it to go directly to the case's Shepards report. If there is no icon, click on the link on the right that says "Shepardize this document". This will show you a list of all cases and other sources that have discussed this case in some substantial way, how much they discussed it, and the nature of the analysis.
Using citators in print:
Print citators are rarely used these days, since this information has largely moved online. However, if you do not have access to Westlaw or Lexis, you may need to use a print citator set to find out whether your case is still good law. Most large law school libraries will have a print citator set and can show you how to use it.
Treatises are books or sets of books that summarize and analyze a particular area of law. If you're just starting your research, you might use a treatise to familiarize yourself with the basic law on your topic or in your jurisdiction. Many treatises will discuss the major statutes and case law governing a legal topic, so checking a treatise can be a good way to get citations to the most significant cases in the field. You can then look up these cases on Westlaw or Lexis or in a print digest, find out what topic and key numbers or headnotes they've been assigned, and look those up in order to locate other cases on the same topics.