Federal Tax Research

A citator is a tool that provides the subsequent history and treatment of a legal authority. They allow you to understand how a particular statute, regulation, or case has been interpreted and applied by other authorities, and they can help you determine whether a case is still good law. For example, if you're looking at a case, a citator can help you determine whether the case has been affirmed, reversed, overruled, or questioned by later cases. It can also show you how the case has been cited in other cases, statutes, regulations, and secondary sources.

The major legal research platforms each offer their own citator service: Westlaw has KeyCite, Lexis has Shepard's, and Bloomberg Law has BCite.

To use a citator effectively, start by finding the citator entry for the authority you're interested in. You can usually do this by pulling up the authority on your legal research platform and then clicking on the citator symbol or link. Once you're in the citator, look for the following information:

• Subsequent History: This will tell you what happened to the specific case after it was decided. For example, if a case was appealed to a higher court, the citator will tell you the outcome of the appeal.
• Citing References: This will show you other authorities that have cited the authority you're looking at. For each citing reference, the citator will provide a brief summary of how the authority was cited.
• Treatment Symbols: These symbols indicate how the authority was treated by the citing references. For example, a red or yellow symbol might indicate that the authority was questioned or criticized, while a green symbol might indicate that it was followed. Citators are not infallible, and a good researcher will double-check the citator's analysis for themself before relying on material.

Remember, while citators are a powerful tool for understanding the significance of a legal authority, they are not a substitute for reading the authorities themselves. Always be sure to read and understand the authorities that are relevant to your research.