In United States constitutional law, the penumbra includes a group of rights derived, by implication, from other rights explicitly protected in the Bill of Rights., Penumbra: Definition; see also Brannon P. Denning & Glenn Harlan Reynolds, Comfortably Penumbral, 77 1089, 1092 (1997) (discussing definition of "Penumbral Reasoning"). These rights have been identified through a process of "reasoning-by-interpolation", where specific principles are recognized from "general idea[s]" that are explicitly expressed in other constitutional provisions.Glenn H. Reynolds, Penumbral Reasoning on the Right, 140 1333, 1334–36 (1992); see also J. Christopher Rideout, Penumbral Thinking Revisited: Metaphor in Legal Argumentation, 7 J. ALWD 155, 155–56 (2010). Although researchers have traced the origin of the term to the nineteenth century, the term first gained significant popular attention in 1965, when Justice William O. Douglas's majority opinion in Griswold v. Connecticut identified a right to privacy in the penumbra of the constitution.See Griswold v. Connecticut, ; Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 81, 83–84 (1987) (discussing origins of the term).

Origins of the term Commentators disagree about the precise origin of the use of the term penumbra in American legal scholarship, but most believe it was first used in the late nineteenth century.Compare Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 478–81 (2011) and Henry T. Greely, A Footnote to "Penumbra" in Griswold v. Connecticut, 6 251 (1989) with Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 81 (1987). Burr Henly, for example, traces the first use of the word to an 1873 law review article written by Oliver Wendell Holmes, in which he argued that it is better for new law to grow "in the penumbra between darkness and light, than to remain in uncertainty".Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 Hastings Const. L. Q. 81, 83–84 (1987) (quoting Holmes, The Theory of Torts, 7 652, 654 (1873), reprinted in 44 773, 775 (1931)). Luis Sirico and Henry T. Greely, on the other hand, trace the term to Justice Stephen Johnson Field's 1871 circuit court opinion in Montgomery v. Bevans, where Justice Field used the term to describe a period of time in which it was uncertain whether an individual could legally be considered deceased.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 478–79 (2011) (citing Montgomery v. Bevans, 17 F. Cas. 628, 632 (C.C.D. Cal. 1871) (No. 9735)); Henry T. Greely, A Footnote to "Penumbra" in Griswold v. Connecticut, 6 251, 252-53 (1989) (noting "its first use in 1871"). Other commentators, including Glenn H. Reynolds and Brannon P. Denning, note that elements of penumbral reasoning can be found in much older cases that precede the first use of the term penumbra; they trace the origins of penumbral reasoning to United States Supreme Court cases from the early nineteenth century.Glenn H. Reynolds, Penumbral Reasoning on the Right, 140 1333, 1343–45 (1992) (citing Crandall v. Nevada, 73 U.S. (6 Wall.) 35 (1868); McCulloch v. Maryland, 17 U.S. (4 Wheat.) 316 (1819)). For example, Reynolds and Denning describe Chief Justice John Marshall's opinion in McCulloch v. Maryland as "the quintessential example of penumbral reasoning".Brannon P. Denning & Glenn Harlan Reynolds, Comfortably Penumbral, 77 1089, 1092–93 (1997)

Definition

Although the meaning of the term has varied over time,Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 481 (2011) (discussing evolution in the term's definition prior to Griswold v. Connecticut). scholars now generally agree that the term refers to a group of rights that are not explicitly stated in the constitution, but can be inferred from other enumerated rights.Brannon P. Denning & Glenn Harlan Reynolds, Comfortably Penumbral, 77 1089, 1092 (1997) (discussing contemporary understanding of the term). The definition of the term was originally derived from its primary scientific meaning, which is "a space of partial illumination (as in an eclipse) between the perfect shadow on all sides and the full light". By analogy, rights that exist in the constitution's penumbra can be found in the "shadows" of other portions of the constitution.See Alex Kozinski & Eugene Volokh, A Penumbra Too Far, 106 1639, 1657 (1993). Additionally, the process of identifying rights in constitutional penumbras is known as penumbral reasoning.Julia Halloran McLaughlin, DOMA and the Constitutional Coming Out of Same-Sex Marriage, 24 145 (2009) Brannon P. Denning and Glenn H. Reynolds have described this interpretive framework as the process of "drawing logical inferences by looking at relevant parts of the Constitution as a whole and their relationship to one another."Brannon P. Denning & Glenn Harlan Reynolds, Comfortably Penumbral, 77 1089, 1092 (1997) Glenn H. Reynolds has also characterized penumbral reasoning as a process of "reasoning-by-interpolation" where judges identify the full scope and extent of constitutional rights.Glenn H. Reynolds, Penumbral Reasoning on the Right, 140 1333, 1334–36 (1992).

Definitions prior to Griswold v. Connecticut The term penumbra first appeared in an opinion published by the Supreme Court of the United States in 1916,Sirico identifies Hanover Star Milling Co. v. Metcalf, 240 U.S. 403, 426 (1916) (Holmes, J., concurring), as the first appearance of the term in an opinion published by the Supreme Court of the United States. See Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 479 (2011). and the term appeared ten more times in published opinions between 1916 and 1941.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 480–81 (2011) (providing statistics between 1916 and 1941). Between 1941 and the date of publication of Griswold v. Connecticut, the term was used eight times by Justice William O. Douglas and four times by other Justices.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 480–81 (2011) (providing statistics between 1941 and 1965). Second Circuit Court of Appeals Judge Learned Hand also used the term eleven times between 1915 and 1950, usually to place emphasis on words or concepts that were ambiguous.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 480 (2011). In these eleven opinions, Sirico also includes opinions written by Judge Hand in the United States District Court for the Southern District of New York. For example, in Commissioner v. Ickelheimer, Judge Hand wrote, "[t]he colloquial words of a statute have not the fixed and artificial content of scientific symbols; they have a penumbra, a dim fringe, a connotation, for they express an attitude of will, into which it is our duty to penetrate and which we must enforce ungrudgingly when we can ascertain it, regardless of imprecision in its expression".Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 480 (2011) (citing Comm'r v. Ickelheimer, 132 F.2d 660, 662 (2d Cir. 1943) (Hand, J., dissenting)).

Before Griswold, different Supreme Court Justices would often utilize different definitions of the term in different contexts, possibly because the Justices did not understand the meaning of the word.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 482 (2011) (discussing hypotheses for why different definitions emerged). In Schlesinger v. Wisconsin, for example, Justice Oliver Wendell Holmes used the term to describe rights derived by implication.Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 81, 87 (1987) (describing Justice Holmes' references to "a protective penumbra created by certain provisions of the Bill of Rights"). He wrote, "the law allows a penumbra to be embraced that goes beyond the outline of its object in order that the object may be secured".Schlesinger v. Wisconsin, (Holmes, J., dissenting). Likewise, in Olmstead v. United States, Justice Holmes argued that evidence obtained through wire-tapping should not be admitted at trial, and that "the penumbra of the Fourth and Fifth Amendments covers the defendant".Olmstead v. United States, (Holmes, J., dissenting) (citation omitted). However, in A.L.A. Schecter Poultry Corp. v. United States, Justice Benjamin Cardozo used the term to describe an area of uncertainty in the law.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 480 (2011) (noting that Justice Cardozo "used 'penumbra' to refer to an area of indeterminacy in the law"); see also Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 81, 88 (1987) (describing Justice Cardozo's use of the term to refer to "an area of uncertainty"). He wrote, "[t]here is no penumbra of uncertainty obscuring judgment here. To find immediacy or directness here is to find it almost everywhere".A.L.A. Schecter Poultry Corp. v. United States, (Cardozo, J., concurring). Additionally, in Coleman v. Miller, Justice Felix Frankfurter used the term in a manner that was more closely related to its traditional definition.Louis J. Sirico Jr., Failed Constitutional Metaphors: The Wall of Separation and the Penumbra, 45 459, 481 (2011) (discussing Justice Frankfurter's use of the term). When arguing that a group of legislators lacked standing, he wrote, "[n]o doubt the bounds of such legal interest have a penumbra which gives some freedom in judging fulfillment of our jurisdictional requirements".Coleman v. Miller, (Frankfurter, J., concurring).

Definition after Griswold v. Connecticut

J. Christopher Rideout and Burr Henly note that the term achieved prominence after Justice Douglas' majority opinion in Griswold v. Connecticut held that a right to privacy existed in the penumbra of the constitution.J. Christopher Rideout, Penumbral Thinking Revisited: Metaphor in Legal Argumentation, 7 J. ALWD 155, 156 (2010); see also Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 81, 83 (1987) ("Commentators sometimes discuss Douglas' Griswold penumbra as if the metaphor had never before appeared in American jurisprudence."). In Griswold, the Supreme Court ultimately held that a Connecticut law that criminalized the use of contraception was unconstitutional.Griswold, 381 U.S. at 482–83. Writing for a majority of the Court, Justice Douglas held that the Connecticut law violated a fundamental right to privacy. After reviewing a line of cases in which the Supreme Court identified rights not explicitly enumerated in the constitution, Justice Douglas declared that "[t]he foregoing cases suggest that specific guarantees in the Bill of Rights have penumbras, formed by emanations from those guarantees that help give them life and substance". Justice Douglas argued that the Court could infer a right to privacy by looking at "zones of privacy" protected by First, Third, Fourth, Fifth, and Ninth Amendments:

Consequently, Justice Douglas argued that the constitution included "penumbral rights of privacy and repose."Griswold, 381 U.S. at 485 (internal quotations omitted). Justice Douglas also remarked that without "peripheral rights," the "specific rights" enumerated in the constitution would be "less secure".Griswold, 381 U.S. at 479, 482, 484. According to Burr Henly, Justice Douglas' majority opinion did not use the term to identify the articulable boundaries of language and the law, as Justice Holmes had done, but rather to connect the text of the constitution to unenumerated rights.Burr Henly, "Penumbra": The Roots of a Legal Metaphor, 15 81, 96 (1987).

Scholarly analysis of penumbral reasoning