Shepardizing

Shepardizing is the process of checking a case citation using Shepard's Citations — the LexisNexis citator system — to verify that the case remains valid authority. The term derives from Frank Shepard, who developed the original case citation tracking system in the 1870s as a paper-based tool for lawyers to identify which cases had been affected by subsequent judicial decisions. LexisNexis acquired the Shepard's system and has maintained it as a core component of its legal research platform.

When a lawyer "shepardizes" a case, they access Shepard's Citations to see the subsequent history of the case (appeals, remands, related proceedings) and the treatment the case has received from later courts (followed, distinguished, criticized, overruled, questioned, limited, and other categories). The system uses signal indicators — a red stop sign icon for serious negative treatment, a yellow caution sign for some negative treatment, a green checkmark for positive treatment — to provide at-a-glance validity information.

While "shepardizing" technically refers to using the Shepard's system specifically, the term has entered common legal parlance as a generic verb for the broader process of citator verification — similar to the way "Googling" has become generic for internet searching. A lawyer who says "I shepardized that case" may mean they used either Shepard's or Westlaw's equivalent KeyCite system. Professional norms distinguish between the brand and the practice, but colloquial usage conflates them.

Shepardizing is a foundational step in legal research that predates computers by over a century — which gives some indication of how long the professional obligation to verify case validity has existed. In the pre-digital era, Shepard's Citations were published as paper volumes that law libraries updated with supplements; checking a case required flipping through multiple volumes and verifying that no supplement had added negative treatment. The digital transition to Lexis made real-time citator checking far more practical.

The AI era has made the verification step simultaneously more important and more automated. More important because AI-generated research can surface cases that do not exist or cite cases for incorrect propositions — creating heightened verification obligations. More automated because AI research platforms increasingly integrate citator signals directly into their outputs, reducing the friction of checking.

The professional responsibility dimension is unambiguous. Model Rule 3.3 prohibits lawyers from knowingly making false statements of law to a tribunal; relying on overruled authority without checking its validity status — particularly when the tools to check are readily available — can constitute a violation. Courts have sanctioned lawyers for citing overruled authority, and several bar associations have issued guidance emphasizing citator verification as a competency requirement.

Lexis+ AI integrates Shepard's Citations directly into its AI research workflow. When the AI generates research citing cases, each citation includes the relevant Shepard's signal, and the user can access the full Shepard's report with a click. This integration prevents the scenario where AI-assisted research bypasses the verification step that was standard in traditional research workflows.

Beyond integration of existing citator data, AI is being applied to improve the underlying citator analysis. Traditional treatment classification — determining whether a citing opinion "follows," "distinguishes," or "criticizes" the cited case — is done by editorial staff reviewing citing opinions. NLP-based systems can potentially perform this classification at scale, identifying the nature of treatment more precisely and more comprehensively than purely manual editorial processes.

For lawyers, the practical implication is that shepardizing should never be understood as optional because an AI tool performed the research. Regardless of how a case was found — through traditional research, AI-assisted search, or AI generation — the verification obligation applies before any citation is included in a brief or opinion.