Center for Advanced Study & Research on Innovation Policy


CASRIP Newsletter - Spring/Summer 1998, Volume 5, Issue 2

Anticipation by Inherency or Accident

Under some circumstances, a feature not explicitly disclosed or appreciated in the prior art can anticipate an element of a claim. This article presents an overview of cases that define the circumstances giving rise to anticipation by a feature inherent in the prior art or by an accidental achievement of the same result.


A disclosure that does not expressly describe an element can still anticipate that element by inherency if it would be understood by one of ordinary skill in the art. Glaxo Inc. v. Novopharm Ltd., 52 F.3d 1043, 34 USPQ2d 1565, 1567 (Fed. Cir. 1995), cert. denied, 116 S.Ct. 516. The failure of a reference to mention that which existed is of no consequence if the element must have been present in the prior art. Hughes Aircraft Co. v. U.S., 8 USPQ2d 1580, 1583 (Cl. Ct. 1988).

A. The Inherent Feature Must be Definite and Flow Naturally From the Elements Expressly Disclosed

Inherency may not be established, however, by probabilities or possibilities regarding what may have resulted in the prior art. In re Oelrich, 666 F.2d 578, 212 USPQ 323, 326 (CCPA 1981). In Oelrich, the examiner d educed from data in the application and affidavits supplied by the appellants that a prior art signal generator could inherently produce frequencies in the range required by the claimed system. Because the claim required a means for generating a carrier f requency less than the minimum system resonant frequency, thereby necessitating a particular relationship between the carrier and resonant frequencies, the court held that the required means was not inevitably present in the prior art system. The court qu oted from Hansgirg v. Kemmer, 102 F.2d 212, 214, 40 USPQ 665, 667 (CCPA 1939): "The mere fact that a certain thing may result from a given set of circumstances is not sufficient." See also Ex parte Skinner, 2 USPQ2d 1788 (B PAI 1986).

Hughes Aircraft Co. v. U.S., 8 USPQ2d 1580, 1583 (Cl. Ct. 1988), held that, to be found inherent in an anticipating reference, an unstated element must exist as a matter of scientific fact and flow naturally from the elements expressly disclosed in the prior art reference. In the case before it, the court found that the claim element at issue, requiring a means for achieving a particular result, was "an idea that is a product of reasoning and hindsight. . . . It is only present by virtue of the intervening step of human perception, awareness and understanding." The ability of one skilled in the art to deduce the missing elements from the prior art disclosure of the concept underlying the claim was considered relev ant to obviousness, not anticipation.

B. Inherency Does Not Apply to Obviousness

Consideration of an inherent quality is relevant only to anticipation, not obviousness. Jones v. Hardy, 230 USPQ 1021, 1025 (Fed. Cir. 1984). Jones dealt with the issue of whether the discovery of a use of an inher ent quality of a product well known in the art was unpatentable because of obviousness. The claims at issue were directed to a polystyrene mold having a pattern of artistic relief and a method of constructing a concrete wall using the mold. In the prior a rt, polystyrene was used for simple molds while other materials were used for making designs. The other materials used for designs presented problems of releasability. In finding the invention nonobvious, the court noted that consideration must be given t o the invention as a whole, not the "degree of inventiveness." Moreover, the quality of releasability inherent in the prior use of polystyrene was not relevant to a determination of obviousness.

Additional examples of nonobviousness of a claim to a method of obtaining a benefit inherent in a prior art use are provided by In re Adams, 148 USPQ 743 (CCPA 1966) and In re Caldwell, 138 USPQ 243 (CCPA 1963). In Adams, the claims were directed to a heat transfer method using aerating or foam nozzles to cool cans filled with hot food. The claims were rejected as obvious in view of the use of foam for heat transfer by fire departments or the use of aerated fauc ets for cooling plates in a kitchen sink. The Patent Office argued that heat transfer was inherent in both of these prior art operations. The court responded by acknowledging the inherency of heat transfer in the prior operations, but noted that patentabi lity hinged on the unexpected and unsuggested increase in heat transfer efficiency and not on inherency. In Caldwell, a prior art disclosure of feeding aspirin to rats did not render obvious a claimed method of stimulating growth of ruminants, poul try and swine by feeding aspirin, because the prior art did not suggest that feeding aspirin would stimulate growth.

In In re Naylor, 152 USPQ 106 (CCPA 1966), the issue was whether a process for preparing polybutadienes having particular properties using Ziegler catalysts was rendered obvious by a prior art process for producing other poly butadienes using Ziegler catalysts that, in combination with other prior art teaching, could be modified to produce the particular polybutadienes of the invention. The court found the claimed process nonobvious because it was a process for preparing a par ticular polybutadiene having a particular microstructure and particular properties. The particular product unexpectedly produced by the claimed process could not be ignored. It was immaterial that the particular polybutadiene might be inherent in the comb ined teachings of the prior art if one of skill in the art would not appreciate or recognize that inherent result.

In summary, it may not be a per se rule that inherency does not apply to an obviousness analysis, so much as a logical impossibility, because an inherent feature would have to be suggested in order to contribute to a finding of obviousness. Yet if the feature were suggested, it would not be characterized as "inherent."


Anticipation by inherency is to be distinguished from accidental or unwitting anticipation. The accidental attainment of a claimed invention, without recognition of the result or how it was achieved, was held not an anticipation in Tilghman v. Proctor, 102 U.S. 707, 26 L.Ed. 279 (1880). The Supreme Court considered it "absurd" to find anticipation where the prior art process for purifying fats and oils preparatory to soap-making had produced fat acids in accord ance with the process of the claim at issue because the acids were accidentally and unwittingly produced, without knowledge of what was done or how it was done.

In Eibel Process Co. v. Minnesota & Ont. Paper Co., 261 U.S. 45 (1923), the Court held that a method for increasing production speed of a paper-making machine by tilting the wire cloth sieve 12 inches was patentably disti nguishable over a prior art paper-making machine that tilted the sieve 3 inches in two ways: (1) the wire was tilted for a different purpose; and (2) the degree of pitch was much greater. The Court further held that any increase in speed achieved in the p rior art machine was accidental, unintentional and unappreciated, and therefore did not anticipate Eibel.

Bird Provisions Co. v. Owens Country Sausage, Inc., 568 F.2d 369, 197 USPQ 134 (5th Cir. 1978), provides an example of a process that was anticipated despite a benefit unappreciated in the prior art. In Bird, the paten t at issue claimed a process for producing and preserving pork sausage. The patentee argued that prior users of the same process steps for preparing pork sausage had not appreciated the shelf-life implications. The court stated that this unappreciated ben efit did not avoid anticipation because the discovery of shelf-life implications involved nothing that was new in its use or method of application. Bird Provisions Co., 197 USPQ at 139. This case can be distinguished from Eibel Process Co. a nd Tilghman because here the purpose of the method, preserving sausage, was the same in the claims and in the prior use. The prior users might not have appreciated how the process steps enhanced shelf-life over alternative processes, but those prio r users were intending to produce and preserve sausage by carrying out the process steps.


A compound and all of its properties are inseparable, and patentability of a compound depends on the properties as well as the structure of that compound. In re Papesch, 315 F.2d 381, 137 USPQ 43, 51 (CCPA 1963). The rec itation of a newly discovered function or property, inherently possessed by things in the prior art, does not cause a claim drawn to those things to distinguish over the prior art. In re Swinehart, 439 F.2d 210, 169 USPQ 226, 229 (CCPA 1971). Thus, for compounds and devices, whether an element's presence is inherent or accidental makes no difference to a determination of novelty. The fact that the unappreciated element was present in the prior art was sufficient to put the public in possession of t he invention.


If a claimed method comprises steps identical to those of a method practiced in the prior art, and the same result would have been achieved in the prior art method, the accidental or unwitting achievement of that result cannot const itute anticipation. In re Marshall, 578 F.2d 301, 198 USPQ 344 (CCPA 1978). In Marshall, the claims were directed to a weight control process comprising the administering of an anesthetic such as oxethazaine to inhibit release of hormones, thereby preventing release of pancreatic enzymes that would otherwise digest food passing through the digestive tract. The cited reference was the Physician's Desk Reference (PDR), which disclosed use of oxethazaine for treatment of esophagitis, gastritis , peptic ulcer and irritable colon syndrome, and disclosed that this anesthetic inhibited release of the acid-stimulating hormone, gastrin. The CCPA held that the PDR did not disclose every material element of the claimed subject matter because the claims were directed to a weight control process and nothing in the PDR remotely suggested taking oxethazaine to lose weight. The court added that "[i]f anyone ever lost weight by following the PDR teachings it was an unrecognized accident."

If an unappreciated feature of a prior art process is merely the inventive concept which makes the process operate as claimed, the failure of the prior art to disclose this feature is not sufficient to avoid anticipation. Verdega al Brothers Inc. v. Union Oil Co. of California, 814 F.2d 625, 2 USPQ2d 1051, 1054 (Fed. Cir. 1987), cert. denied, 108 S.Ct. 95. In Verdegaal, the claim at issue was directed, as recited in the preamble, to a process for making a concent rated liquid fertilizer by reacting sulfuric acid and urea. The prior art reference disclosed all the process steps as well as the features of the preamble of the claim. The prior art reference had failed to explicitly identify the heel required in step ( a) of the process as a heat sink, which was argued to be the inventive concept. The court maintained that this property was inherently possessed by the heel in the prior art process, and thus the claimed process was anticipated. Verdegaal can be di stinguished from Marshall because the feature allegedly unappreciated in the prior art process, the provision of a heat sink, was not the purpose identified in the process claim at issue. Rather, the prior art process literally met all elements of the claim.

A process claim is anticipated by a prior art device which, in its normal and usual operation, will perform the claimed function. In re Ackenbach, 7 USPQ 268 (CCPA 1930). In re King, 231 USPQ 136 (Fed. Cir. 1986) held that a prima facie case of anticipation had been established by the Board's finding that a prior art device performed the function disclosed in the method claim at issue when that device was used in normal and usual operation. In a footnote, howeve r, the court in King mentioned that it could not consider the "accidental use doctrine" because that argument was not properly before it, leaving open the possibility that appreciation of the result could make a difference. In addition, t he claim at issue in King was directed to a "method of enhancing in a predetermined way color effects produced by ambient light while controlling light intensity produced thereby." The prior art reference stated that the thickness of its reflective layer and the thickness and composition of its metal oxide layer could be varied to achieve different reflectance and transmittance characteristics and colors. Thus, it did not appear that the object of the claimed method was not appreciated in the prior art.

In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990) drew a distinction between discovering a completely new use for an old compound and discovering a new benefit of an old process. In Woodruff, the claims we re directed to a process for inhibiting the growth of fungi on fresh leafy and head vegetables. A prior patent taught the same process steps for preventing the deterioration of fresh vegetables, referring specifically to effectiveness against respiratory, bacterial, and enzymatic deterioration. The Federal Circuit characterized the prior use as a generic one that "certainly encompasses the specific benefit disclosed by Woodruff," and held that the newly disclosed benefit could not render the cla imed process patentable. The language used by the court suggests that, with regard to the purpose achieved by a process claim, a generic disclosure may anticipate a specific claim. It may be that unexpected advantages to the specific purpose must be demon strated to avoid anticipation by a generic process.


Anticipation by inherency or by accident must be considered differently with respect to methods as compared to compounds and devices. The consistent principle is that a benefit already provided to the public cannot be removed by discovery of an additional feature. Further advantages of a known compound or device do not increase what is already in the public domain. In contrast, appreciation of a previously unknown result achieved by an old method puts the public in possession of a new use. A method that has been practiced in the prior art, but without appreciation of a specific result, is not sufficient to anticipate a method for achieving that same unappreciated result. A method for achieving a specific result can be anticipate d, however, by prior use of the same process steps for a purpose generic to the specific result.

Dr. Karen Canady

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