Definition
To err, in legal usage, means to make a mistake or commit an error — specifically, to deviate from what is legally correct. The term appears most commonly in appellate practice: a court or tribunal is said to have "erred" when it made a ruling, finding, or instruction that was legally incorrect. The verb form is the foundation of the noun "error," which names the mistake itself and gives appellate doctrine much of its vocabulary.
Used in argument: a party "assigns error" to a lower court's ruling, contending the court erred in admitting evidence, instructing the jury, or applying a legal standard. The phrase "the court below erred" is the essential predicate of appellate review.
Common Language
Modern common usage (Wiktionary): To make a mistake; to sin; to stray.
Historical common usage (Webster's 1913): To wander, roam, or stray (archaic); to deviate from a true course; to fall into intellectual mistake or error.
The common and legal meanings share a core — deviation from correctness — but the legal usage is narrower and more procedural. In law, to err is not merely to be wrong; it is to be wrong in a way that may be cognizable on review. A judge who "errs" has made a mistake that the legal system has a mechanism to address. The moral or spiritual overtone present in the common meaning (to sin, to stray from righteousness) is entirely absent from legal usage.
Common Confusion
"Err" and "error" are grammatically distinct but functionally intertwined in legal writing, and researchers sometimes treat them as interchangeable index terms when searching historical sources. They are not. Err is the verb; error is the noun that names the cognizable mistake. More importantly, Burrill's entry (see Historical Dictionary Support, below) assigns err a different, specialized meaning — one unrelated to mistake-making — which creates a potential trap for researchers relying on historical dictionary sources.
Why It Matters in Research
The primary research trap here is Burrill's entry. Burrill treats "err" not as a verb meaning "to mistake" but as a term of doubtful or ambiguous signification, cross-referencing Equivocum. This is a rare, narrow technical use — a term characterized as "erring" or "wandering" in its meaning, not a term describing a party or court's mistake. A researcher finding this entry and assuming it represents the dominant legal meaning of the word will be misled. Burrill's entry reflects a specialized descriptive use from older jurisprudence about ambiguous language in instruments; it is not a definition of how "err" functions in appellate practice.
For practical research into appellate doctrine — which is where "err" appears most — the operative vocabulary is built around "error," not "err" itself. Researchers should index under: error, harmless error, reversible error, plain error, invited error, and assignment of error. The verb "err" will surface in judicial opinions and briefs as a predicate, but the doctrine lives under the noun.
Jurisdictionally, the standard of review governing whether a court "erred" varies considerably — abuse of discretion, de novo, clearly erroneous — and the consequence of finding error depends on whether the error was preserved, harmless, or plain. Searching for "erred" without attention to the reviewing standard will retrieve cases applying very different rules.
Historical Dictionary Support
Burrill's Law Dictionary offers a striking departure from what modern researchers would expect. Rather than defining "err" as a verb meaning to make a legal mistake, Burrill treats it as a term applied to words or instruments of doubtful or wandering signification, directing the reader to "Equivocum." This reflects the older Latin-influenced legal vocabulary in which a term could be described as "erring" — ambiguous, unresolved, capable of multiple readings — borrowing from the common-law Latin and the word's root meaning of wandering or straying rather than its modern meaning of mistake-making.
Webster's 1913 confirms this dual history: the word carried both a literal sense of physical wandering (archaic by 1913) and an intellectual sense of falling into mistake. The legal tradition, via Burrill, preserved the wandering sense in a specialized technical application long after ordinary English had moved on.
No other source dictionary was provided for this entry. The absence of Bouvier, Black's, or other major dictionaries from the source set limits cross-comparison. Researchers should note that Black's Law Dictionary, in its various editions, treats "error" extensively but does not typically feature "err" as a standalone headword — consistent with the practical reality that the verb lacks its own developed doctrine.
Jurisdictional Note
The legal consequences of finding that a court "erred" are jurisdictionally variable. Federal courts apply the harmless error standard of Federal Rule of Civil Procedure 61 and Federal Rule of Criminal Procedure 52; state standards differ. Whether error must be preserved below to be cognizable on appeal is a near-universal rule, but its application varies in strictness across jurisdictions.