Definition
OPINION has three principal legal meanings, each operating in a distinct doctrinal context.
1. Judicial Opinion. A court's written explanation of its decision in a case, setting out the legal reasoning, analysis of facts, and applicable rules that led to the judgment. A judicial opinion may be issued by a single judge or by a multi-member court. Where a majority agrees on both the outcome and the reasoning, the result is a majority opinion binding as precedent. Where judges agree on the outcome but not the reasoning, the result is a plurality opinion. Separate concurrences and dissents accompany many appellate decisions.
2. Opinion Evidence (Evidentiary Sense). A witness's inference, conclusion, or judgment drawn from observed facts, as distinguished from direct testimony about facts the witness personally perceived. The law has historically disfavored lay opinion testimony on the theory that drawing inferences from facts is the jury's function. Modern evidence rules permit lay opinion where it is rationally based on the witness's perception, helpful to the fact-finder, and not based on specialized knowledge. Expert opinion — the inference of a qualified specialist — is governed by a separate framework permitting testimony on matters beyond common knowledge, including the ultimate issue in the case.
3. Legal Opinion (Professional Sense). A formal written statement by an attorney or other legal professional setting out a legal conclusion on a specific question — typically offered to a client, counterparty, or third party as a basis for reliance. Common in transactional practice (opinion letters confirming enforceability of agreements, legality of securities offerings, and the like). Distinct from judicial opinions and from informal advice.
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Common Language
Modern common usage (Wiktionary): A belief, judgment, or perspective that a person has formed, either through objective or subjective reasoning, about a topic, issue, person, or thing.
Historical common usage (Webster's 1913): That which is opined; a notion or conviction founded on probable evidence; belief stronger than impression, less strong than positive knowledge; settled judgment in regard to any point of knowledge or action.
The gap matters. In ordinary English, "opinion" is personal and informal — what someone thinks or believes. In its evidentiary sense, legal opinion is not synonymous with personal belief; it is an inference drawn from perceived facts and is subject to strict admissibility rules that the common definition would not suggest. In its judicial sense, a court's "opinion" is not a belief open to question but a legally authoritative statement of the reasons for a binding judgment.
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Common Confusion
Two distinctions recur in research:
Opinion vs. Judgment. The opinion is the court's explanation of its reasoning; the judgment (or decree) is the court's actual command or disposition — who wins, what relief is granted. These are separate documents and carry different legal weight. A court's judgment is enforceable; its opinion, strictly speaking, is not — it is the reasoning that supports the judgment and may become precedent.
Lay Opinion vs. Expert Opinion. These terms share a word but are governed by entirely different rules and standards. A researcher conflating them will misread both historical treatises and modern rules of evidence. The historical sources below largely address lay opinion; the modern framework for expert opinion developed substantially later, particularly through codified rules of evidence in the twentieth century.
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Recognized Forms
/SUBTYPES
Judicial Opinions:
- Majority Opinion: Agreed upon by more than half the court; controls as precedent.
- Plurality Opinion: Most votes of any single position, but short of a majority on reasoning; precedential weight is contested and jurisdiction-dependent.
- Concurring Opinion: Agrees with the outcome, disagrees with or supplements the majority's reasoning.
- Dissenting Opinion: Disagrees with the outcome and often the reasoning; not precedent, but influential in later doctrinal development.
- Per Curiam Opinion: Issued in the name of the court as a whole, without attribution to an individual author.
- Advisory Opinion: A legal conclusion rendered without a live case or controversy. Federal courts are constitutionally prohibited from issuing advisory opinions; many state courts may render them in defined circumstances.
Opinion Evidence:
- Lay Opinion: Non-expert witness inference, governed in federal courts by FRE 701.
- Expert Opinion: Specialist inference, governed by FRE 702–705 and the standards developed in the federal courts for reliability and qualification.
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Why It Matters in Research
The word "opinion" in historical sources almost always refers to evidentiary opinion — witness testimony as inference — not to judicial decisions. A researcher searching historical dictionaries or treatises for commentary on judicial opinions will find little; the doctrinal apparatus for judicial opinions as precedent-setting documents developed separately in case law and appellate practice treatises. Do not assume that a historical source's silence on judicial opinions signals anything other than a different frame of reference.
In the evidentiary context, the baseline rule excluding lay opinion is older than the exceptions. Historical sources reflect a world with no codified expert witness doctrine; the modern expert witness framework (including reliability gatekeeping) postdates them entirely. Any historical dictionary entry on opinion evidence must be read against this gap.
For judicial opinions specifically: the distinction between opinion and judgment is critical to understanding citation practice. Courts issue opinions; parties enforce judgments. Conflating them is a persistent research error, especially when reading older equity decisions where the chancellor's decree and the written reasoning appeared in forms that did not map cleanly onto modern practice.
Advisory opinions appear in a distinct constitutional research context. At the federal level, Article III's case-or-controversy requirement bars federal courts from rendering advisory opinions. State courts vary significantly. Researchers working in pre-twentieth-century state materials will encounter advisory opinion practice in jurisdictions that have since curtailed or abolished it.
Legal opinion letters are researched through transactional practice materials and bar association guidance, not through the same channels as judicial or evidentiary opinions. The three meanings of OPINION draw on largely separate bodies of authority.
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Historical Dictionary Support
Black's Law Dictionary and its second edition treat OPINION primarily in the evidentiary sense: an inference or conclusion drawn by a witness from facts some of which are known and others assumed, or from facts that lend probability to the inference without compelling it by necessary reasoning. Both editions acknowledge that an inference necessarily involving certain facts may be stated without itemizing those facts — a recognition that lay shorthand is sometimes the most natural form of testimony.
Bouvier's Law Dictionary similarly grounds its treatment in evidence law, drawing the line between what a witness knows as fact and what the witness concludes or infers. Bouvier captures the underlying rationale: drawing inferences from facts is the jury's function, and permitting witnesses to testify to their judgments risks substituting the witnesses' verdict for the jury's. Bouvier also notes the necessity exception for matters of science, art, or trade — the precursor to the modern expert witness rule — correctly identifying that specialized knowledge can give a witness's inference a value beyond that of any ordinary inference.
Anderson's Dictionary of Law and the retrieved Bouvier entries on point are not directly on OPINION in its judicial or professional senses. This reflects the historical orientation of these sources toward trial practice and evidence rather than appellate doctrine.
None of the historical sources address judicial opinions as a distinct legal category, and none anticipate the professional legal opinion letter as a transactional instrument. Researchers using these sources should treat them as authoritative on evidentiary opinion and as silent — not wrong — on the other two meanings.
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Jurisdictional Note
The evidentiary rules governing lay and expert opinion vary between federal courts (FRE 701–705) and state courts, though many states have adopted rules modeled on the federal rules. Advisory opinion practice varies sharply by state: some state supreme courts may render advisory opinions to the legislature or governor; federal courts may not. The weight of plurality judicial opinions as precedent is a jurisdiction-by-jurisdiction question with no uniform national rule.
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Encyclopedia Cross-Reference
Lay Opinion Testimony — Rule 701 (The Law Mind Civil Procedure & Evidence Encyclopedia)
Expert Opinion on Ultimate Issue — Rule 704 (The Law Mind Civil Procedure & Evidence Encyclopedia)
Advisory Opinions and the Case-or-Controversy Requirement (The Law Mind Constitutional Law Encyclopedia)
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