In legal research, a citator is a tool that tracks what has happened to a court decision, statute, or regulation after it was published. It compiles every later source that references the original — appellate rulings in the same case, later decisions in other cases, amendments, repeals, law review articles — and classifies that activity so you can tell at a glance whether the authority is still good law. Without a citator, you have no reliable way to know that the 2010 case you want to cite was narrowed in 2018 and gutted in 2023.
What a Citator Does
Enter a case citation and the citator returns a report showing the full trail of subsequent activity for that case: appeals, later decisions that applied or rejected its reasoning, statutes that codified or overrode its holding, and secondary sources that analyzed it. The same process works for statutes and regulations. A citator report for a statute shows whether it has been amended, repealed, or challenged as unconstitutional.
The practical value is straightforward. Legal authority has a shelf life, and tracking its status by hand would mean reading every subsequent case in the relevant jurisdiction. Citators automate that work and flag the results with visual indicators so you can assess validity quickly.
What You See in a Citator Report
A citator report packs a lot of information into one view. Knowing which section answers which question keeps you from either missing a red flag or wasting time on citing references that don’t matter.
Direct History
Direct history tracks the procedural life of the case itself — the chain of events involving the same parties and the same dispute. It tells you whether the trial court was affirmed, reversed, or sent back for a new trial on appeal, and it captures prior history from the lower court. This is where you learn whether your case is still good law in the most literal sense. A reversal on appeal means the holding you planned to cite was rejected by a higher court with authority over it.
Indirect History and Citing References
Indirect history shows how other courts, in cases with different parties, have treated your authority. A case can survive its direct history intact but still lose persuasive weight if later courts have criticized its reasoning or confined its holding to narrow facts. Citing references extend beyond court opinions to include law review articles, treatises, and attorney general opinions.
Treatment Signals
Every major citator uses color-coded signals to give an immediate read on the status of an authority. The systems differ slightly between services, but the general logic is consistent:
- Red indicates strong negative treatment. The case has been reversed on appeal, overruled by a later decision, or (for statutes) declared unconstitutional. At least one point of the case is no longer good law.1Thomson Reuters Law Blog. Checking Cases with KeyCite
- Orange, used by Shepard’s, means the validity of the case has been questioned, often because intervening circumstances like legislative changes have undermined its reasoning.2LexisNexis. Shepards Signals and Analysis
- Yellow indicates possible negative treatment. The case has been criticized or distinguished, but it hasn’t been formally overruled.1Thomson Reuters Law Blog. Checking Cases with KeyCite
- Green indicates positive treatment. The case has been affirmed or followed by later courts.2LexisNexis. Shepards Signals and Analysis
These signals are starting points, not conclusions. A yellow flag does not automatically mean you cannot cite the case; it means you need to read the citing references to understand exactly what was criticized and whether it affects the proposition you’re relying on. Even a red-flagged case may have holdings that remain intact if only one issue was reversed.
Depth of Treatment
Not all citing references engage with your case in the same way. Some courts discuss it at length, while others drop it into a string citation without analysis. KeyCite addresses this with a depth-of-treatment rating that ranks how extensively a citing case engaged with the original. The scale runs from “examined,” meaning the citing case devoted extended discussion to the original, down through “discussed,” “cited,” and “mentioned,” which indicates little more than a passing reference.3Westlaw. KeyCite at a Glance When a report has hundreds of citing references, sorting by depth of treatment surfaces the ones worth reading first.
What the Treatment Terms Actually Mean
The color signals tell you something is wrong. The treatment terms tell you what, specifically, happened — and these terms carry different weight. Confusing them can lead you to abandon usable authority or rely on authority that has been fatally undermined.
- Overruled: a later court explicitly rejected the holding. This is the most severe negative treatment.4LexisNexis. Shepards Signal Indicators and Analysis Phrases
- Abrogated: a later court effectively departed from the reasoning without saying “we overrule this.” The practical effect is similar to being overruled, but the language is less direct.4LexisNexis. Shepards Signal Indicators and Analysis Phrases
- Superseded: a legislative or administrative action replaced the authority. For statutes, this means the legislature passed a new law covering the same ground.4LexisNexis. Shepards Signal Indicators and Analysis Phrases
- Distinguished: a later court found the facts or legal issues different enough that the original case didn’t control. The original isn’t rejected; it just doesn’t apply to the new situation.4LexisNexis. Shepards Signal Indicators and Analysis Phrases
- Criticized: a later court disagreed with the reasoning but lacked authority to overrule the decision. The case remains technically valid but is weakened as persuasive authority.4LexisNexis. Shepards Signal Indicators and Analysis Phrases
The distinction between “overruled” and “distinguished” is the one that trips up newer researchers most often. A distinguished case is not bad law. It simply didn’t apply to different facts. If your facts sit closer to the original case than to the distinguishing case, the original authority may still support your argument.
How to Use a Citator
Start by entering your case citation, statute section, or regulation number into the citator’s search field. The report loads with the treatment signal in view. If the signal is red, read the direct history immediately to pinpoint what was reversed or overruled. If it’s yellow or orange, open the citing references and see whether the negative treatment touches the specific legal point you care about.
Filtering is where citators save serious time. Most services let you narrow citing references by jurisdiction, court level, date range, and type of treatment. Arguing in a federal district court in the Ninth Circuit? Filter to see only how Ninth Circuit courts have treated your authority. Both Shepard’s and KeyCite also let you filter by headnote or legal topic, so you can isolate citations addressing the specific issue in your case rather than wading through references to unrelated portions of the same opinion.
One discipline separates thorough researchers from careless ones: always read the actual text of any citing reference carrying negative treatment. The signal tells you something happened. Only the opinion itself tells you whether it matters to your argument.
Why This Isn’t Optional for Lawyers
For practicing attorneys, using a citator is a professional obligation, not a convenience. The ABA Model Rules of Professional Conduct require that a lawyer provide “competent representation,” defined as “the legal knowledge, skill, thoroughness and preparation reasonably necessary for the representation.”5American Bar Association. Rule 1.1 Competence Citing an overruled case without checking falls below that standard.
ABA Model Rule 3.3 goes further, requiring that a lawyer not knowingly “fail to disclose to the tribunal legal authority in the controlling jurisdiction known to the lawyer to be directly adverse to the position of the client.”6American Bar Association. Rule 3.3 Candor Toward the Tribunal A citator is how you find out that adverse authority exists.
Courts have teeth on this issue, too. Under Federal Rule of Civil Procedure 11, every attorney who files a paper certifies that “the claims, defenses, and other legal contentions are warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law.” A court that finds overruled authority was cited in violation of this certification can impose sanctions including monetary penalties, payment of the opposing party’s attorney’s fees, or nonmonetary directives.7Legal Information Institute (Cornell Law School). Federal Rules of Civil Procedure Rule 11 Law firms can be held jointly responsible for violations committed by their attorneys.
Where to Find a Citator
Three subscription platforms dominate citator services in the United States, each with its own interface and editorial approach.
Shepard’s Citations (LexisNexis)
Shepard’s is the oldest citator in American law. Frank Shepard first published it in 1873 as a pamphlet service for Illinois attorneys. The term “Shepardizing” is still used as a generic verb for checking the validity of a citation, regardless of which service you’re actually using. Shepard’s uses the most granular signal system of the three major services, with distinct red, orange, yellow, and green indicators for different levels of treatment.2LexisNexis. Shepards Signals and Analysis
KeyCite (Westlaw)
KeyCite integrates citator information directly into every case and statute on Westlaw. When you open a case, KeyCite tabs at the top show negative treatment, history, and citing references. The depth-of-treatment indicators help prioritize which citing references to read first, and integration with West’s headnote system allows precise filtering by legal topic.1Thomson Reuters Law Blog. Checking Cases with KeyCite
BCite (Bloomberg Law)
Bloomberg Law’s BCite shows the exact language a citing court used, so you can see treatment in context without opening the full opinion.8Bloomberg Law. Litigation Intelligence Center One limitation: Bloomberg Law does not currently offer a headnote system for filtering citing references by legal topic the way Shepard’s and KeyCite do.
Free and Lower-Cost Alternatives
Commercial citators are expensive, and plenty of researchers — recent graduates, solo practitioners, self-represented litigants, journalists — need something else. Several free tools exist, with real limitations.
Google Scholar indexes court opinions and offers a “How Cited” feature listing other cases that reference the one you’re viewing. The Library of Congress notes that it “is not considered to be as authoritative as citators produced by other publishers/subscription resources.”9Library of Congress. Google Scholar – How To Find Free Case Law Online Google Scholar does not provide editorial treatment signals. It shows which cases cite yours; it won’t tell you whether the treatment was positive or negative.
Many state bar associations offer members free access to vLex Fastcase. Fastcase developed a tool called Authority Check and an automated system called Bad Law Bot that uses algorithms to identify likely negative citation history based on the language courts use when citing earlier decisions. The caveat: Bad Law Bot relies on automated analysis rather than human editorial review, so a case overruled without a later court explicitly citing it will not be flagged.10Fastcase. Using Authority Check If you’re a bar member, check whether your state offers this benefit.
The Free Law Project, which operates the CourtListener database, announced in 2025 that it is building an open-source AI-powered citator, though the project describes itself as being in early stages.11Free Law Project. Building a Citator with AI, A Progress Report CourtListener currently offers basic citation linking between opinions but not yet the editorial treatment analysis that makes commercial citators reliable.
Free tools can help you find citing references, but none currently replaces the editorial judgment of Shepard’s, KeyCite, and BCite. If you’re relying on a free tool, budget extra time to read the citing cases yourself and make your own assessment. For anything you plan to file with a court, verifying with a commercial citator remains the professional standard.