Shepardizing vs. KeyCiting: What's the Difference?

"Shepardize" is a Lexis trademark that has drifted into generic use; Shepard's Citations began as printed citator volumes in the nineteenth century and moved onto Lexis. KeyCite is Thomson Reuters' competing citator, built into Westlaw and tied to the West headnote and Key Number system. Both answer the same two questions: (1) what happened to this authority later—was it reversed, overruled, amended, repealed, held unconstitutional, superseded; and (2) who has cited it, and how.

The meaningful differences are operational. Each vendor's attorney-editors independently characterize how a later case treated an earlier one, so one may tag a citation "distinguished" while the other calls it "criticized" or says nothing. Each indexes a different universe of citing documents—Westlaw pulls in its own secondary sources, ALR annotations, and briefs; Lexis pulls in its own treatises, Matthew Bender titles, and law reviews. Neither is a complete map of everything ever written about your case.

Do not treat the choice as a research philosophy. Treat it as a tool you happen to have a license for. In practice you will use whichever database your school, firm, or agency pays for, and on a high-stakes issue you will check both if you can.

The symbols are the most visible difference and the easiest thing to misread. Learn both sets, because a red flag and a red stop sign do not encode identical judgments.

Westlaw's KeyCite uses flags: a red flag means the case is no longer good law for at least one point of law; a yellow flag means there is some negative history or treatment short of reversal or overruling; a blue-and-white striped flag means an appeal is pending; and an orange warning triangle (KeyCite Overruling Risk) means the case itself may be undermined because it relied on authority that has since been overruled. Westlaw also shows depth of treatment on a four-bar scale, from "Examined" down to "Mentioned."

Lexis's Shepard's uses a different vocabulary: a red octagon (stop sign) warns of negative treatment; an orange square with a Q means validity has been questioned by citing references; a yellow triangle signals possible negative treatment or caution; a green diamond with a plus sign indicates positive treatment such as "followed"; a blue circle with an A means citing references with neutral analysis exist; and a blue circle with an i means citing references exist without editorial analysis. Shepard's also assigns analysis phrases—followed, distinguished, criticized, explained, overruled in part—to individual citing decisions.

Signals are editorial opinions generated by human attorney-editors and, increasingly, by algorithms trained on their work. When a later court writes "we decline to extend" or "we are not persuaded by," whether that becomes a yellow flag, a "criticized" tag, or nothing at all is a judgment call, and the two companies make it separately.

Coverage also differs. If the only case criticizing your authority appears in a source one vendor indexes and the other does not, only one citator will show a signal. Unpublished dispositions, tribal court decisions, agency adjudications, and older state trial-level material are indexed unevenly.

The practical rule: never report a signal as your conclusion. The signal is a pointer. Your conclusion comes from reading the negative citing case and deciding whether it touches the proposition you are actually citing the case for.

This is the step most 1Ls skip, and it is the whole value of a citator. A case can carry a red flag because its Fourth Amendment holding was overruled while its contract-interpretation holding remains untouched and widely followed. If you cite it for the contract point, the red flag is noise—but you must be able to prove that.

On Westlaw, open the Citing References tab, then filter by headnote: select the headnote number corresponding to your proposition and see only the cases discussing that point. Sort by depth of treatment and read the ones with three or four bars first, plus anything flagged negative. On Lexis, open Shepard's, then narrow by LexisNexis headnote and by analysis type (limit to Overruled, Criticized, Distinguished, Questioned) to isolate the trouble.

Both platforms also offer a Table of Authorities view, which runs the citator on the authorities your case relied on. Use it when a decision is old: if its foundational precedent collapsed, the case may be dead in substance even without a flag. Westlaw's Overruling Risk triangle automates part of this, but the manual check catches more.

A citator tracks citations. It does not track silence. A decision can be implicitly abrogated by a later Supreme Court opinion that never names it, gutted by a statutory amendment that no court has yet applied, or rendered irrelevant by a rule change. None of that reliably produces a flag.

Citators are also weak on statutes and regulations. A KeyCite or Shepard's report on a statute will show amendments, repeals, and judicial constructions, including holdings of unconstitutionality or preemption, but you still need to confirm the currency date of the code you are reading and check session laws or pending legislation for anything enacted after that date. For regulations, confirm the effective version in the Federal Register or the e-CFR.

Finally, a citator will not tell you the case is factually distinguishable, poorly reasoned, or from a jurisdiction that binds nobody. That is your job.

What you learn from the citator often has to appear in the citation itself. Bluebook Rule 10.7 requires you to give significant prior and subsequent history, using the italicized explanatory phrases collected in Table T8—aff'd, rev'd, vacated, overruled by, abrogated by. Rule 10.7.1 supplies the exceptions: omit denials of certiorari or rehearing unless the denial is recent or particularly relevant, and omit history on remand or in separate proceedings unless relevant to your point. Get the history right and you have simultaneously proven you validated the case.

The duties behind this are not stylistic. Federal Rule of Civil Procedure 11(b)(2) makes your signature a certification that your legal contentions are warranted by existing law or a nonfrivolous argument to change it—citing an overruled case fails that test. ABA Model Rule of Professional Conduct 3.3(a)(2) requires you to disclose directly adverse controlling authority that opposing counsel has not disclosed, and running a citator is often how you find it. Courts have sanctioned lawyers for citing reversed or fabricated authority; the citator is your cheapest insurance.

Learn both, because your access will change. Most ABA-accredited schools give students accounts on Westlaw, Lexis, and often Bloomberg Law, but this varies by school and by year, and vendor training requirements and password expiration policies vary too—check with your research librarian rather than assuming. After graduation, many small firms, public defenders, and government offices carry only one subscription, and some carry only a lower-cost service.

Know the alternatives by name. Bloomberg Law's citator is BCite, which reports a composite analysis plus separate direct-history and case-analysis tabs. Fastcase and vLex offer automated negative-treatment detection. Free tools like Google Scholar and CourtListener show citing documents but do not supply editorial treatment signals, which makes them useful for finding citing cases and inadequate as a sole validation step.