Not every diagnosis patent is invalid under 35 U.S.C. § 101 for being directed to a law of nature. In Exergen Corp. v. Kaz USA Inc., the Federal Circuit ruled that detecting a fever by measuring a patient’s forehead temperature is patentable subject matter. This is in contrast to the patent-ineligible discovery of, for example, how to identify the father of a fetus by drawing the mother’s blood (not amniotic fluid) and then amplifying and analyzing paternal DNA in that blood (Ariosa v. Sequenom).
An analysis of the majority and dissenting opinions, as well as the way the claims at issue in Exergen (and Ariosa) were worded, will hopefully shed light on the court’s reasoning in this rapidly developing area of patent law. Such analysis may also increase the odds of predicting whether a claim will be found to be eligible and how to draft claims that will survive eligibility challenges.
Background — The Patents at Issue
Exergen’s claims at issue were 7, 14 and 17 of U.S. Pat. No. 6,292,685 (the “‘685 patent”) and 17, 24, 33, 39, 40, 46, 49, 60 and 66 of U.S. Pat. No. 7,787,938 (the “‘938 patent”). The patented temperature detectors and methods of detection function by measuring both the ambient temperature and the peak temperature of the patient’s skin over the temporal artery. An algorithm then correlates these readings to provide the approximate core body temperature.
Claim 7 (which depends from claim 4, which depends from claim 1) of the ‘685 patent is a method claim and reads as follows:
 A method of detecting human body temperature comprising: laterally scanning a temperature detector across a forehead; … providing a peak temperature reading from plural readings during the step of scanning…. computing an internal body temperature as a function of ambient temperature and the peak temperature reading…. wherein the temperature detector comprises a radiation sensor which views a target surface area of the forehead.
Claim 39 of the ‘938 patent is a product claim requiring (1) a radiation detector and (2) electronics adapted to perform a temperature detection method. Claim 39 reads as follows:
39. A body temperature detector comprising:
a radiation detector;
electronics that measure radiation from at least three readings per second of the radiation detector as target skin surface over an artery is viewed and that process the detected radiation to provide a body temperature approximation based on heat flow from an internal body temperature to ambient.
Thus, the method of claim 7 and effectively, the product of claim 39, require measuring temperature with a specific device and transforming the readings into a core body temperature value.
After a trial, the jury found the asserted claims to be both infringed and not invalid. Without Kaz’s objection, no factual or legal issues with respect to patent eligibility had been submitted to the jury. The verdict awarded Exergen over $14 million in combined lost profits and reasonable royalties. Kaz moved for judgment as a matter of law, inter alia, with respect to patent eligibility under § 101. This motion was denied.
Patent Eligibility Under 35 U.S.C. § 101
The issue of how to address whether a patent is directed to a law of nature has been lurking in the background for years. As Justice Felix Frankfurter explained in his concurring opinion in Funk Bros. Seed Co. v. Kalo Inoculant Co., 333 U.S. 127, 134-35 (1948)(Frankfurter, concurring), “[i]t only confuses the issue … to introduce such terms as … ‘laws of nature.’… Everything that happens may be deemed ‘the work of nature.’” Notwithstanding Justice Frankfurter’s warning, many claims now effectively undergo two prior art analyses. A first, applies the well-developed case law of 35 U.S.C. §§ 102 and 103; and a second applies the emerging law of patentable subject matter eligibility under 35 U.S.C. § 101.
The U.S. Supreme Court has provided a two-step test for distinguishing between ineligible patents that claim no more than building blocks of nature and patents that integrate those building blocks into eligible subject matter. In step one, a court must “determine whether the claims at issue are directed to a patent-ineligible concept.” If so, in step two, the elements of the claim are assessed to determine whether they contain an “‘inventive concept’ sufficient to ‘transform’ the claimed [natural phenomenon] into a patent-eligible application” of that phenomenon. If the claim features in addition to the natural phenomenon “involve ‘well-understood, routine, [and] conventional activity previously engaged in by researchers in the field, … they do not constitute an ‘inventive concept.”
Exergen did not dispute step one. However, it maintained that the claims added a sufficient inventive concept to satisfy step two. This allegedly involved (1) lateral scanning; (2) obtaining a peak temperature reading; or (3) obtaining at least three readings per second. In response, Kaz argued that these steps were well-known and conventional. The district court sided with Exergen, reasoning that being “known,” in and of itself, was not enough to establish ineligibility under step two. Borrowing from the law of obviousness, the district court first recognized that new combinations of known steps may be nonobvious. Next, it concluded that Exergen’s patents could survive step two because they resulted in a new combination of known steps. Similarly, in Rapid Litigation, the Federal Circuit had found that although the individual steps of freezing, thawing and separating were conventional, the combination of those steps in the claimed method was not. Accordingly, the district court found Exergen’s claims to provide an inventive concept.
Well-Understood, Routine and Conventional
On appeal, the Federal Circuit explained that a district court’s findings are due substantial deference: “[l]ike indefiniteness, enablement, or obviousness, whether a claim is directed to patentable subject matter is a question of law based on underlying facts.” Therefore, “[t]he district court’s conclusion that [Exergen’s] claim elements were not well understood, routine, and conventional was a factual finding” to be reviewed under a “clearly erroneous” standard.
The majority affirmed, reasoning that although each of the claimed measurement steps were known, they were not known for the detection of core body temperature. Moreover, the court explained that just because something is in the prior art, does not mean it is “well” known: “[s]omething is not well-understood, routine and conventional merely because it is disclosed in a prior art reference.” The court asserted that although obscurity does not disqualify a reference from being prior art, that an obscure German thesis stored in a university library does not establish that its teachings were well known and routine.
The majority also explained that the steps should not be reviewed in a isolation, but in the context of the claim as a whole. It concluded that using a radiation detector to measure forehead temperature might be routine, but for detecting injury, not for determining core temperature. The majority explained that the inventors had calculated a heretofore unknown coefficient representing the unknown relationship between temporal-arterial temperature, ambient temperature and core body temperature. The majority then found patent eligibility under step two on the grounds the inventors “incorporated their discovery [of a natural phenomenon] into an unconventional method of temperature measurement.” Therefore, concluded the majority, the claims were patent eligible.
In contrast, Judge Todd Hughes concluded that the district court had applied an incorrect legal standard. First, he argued that all of the claim elements were well-known: “[p]rior art products combined skin scanning, obtaining peak temperatures, and taking multiple temperature measurements per second.” Next, he asserted that the claims “amount to nothing more than using a pre-existing temperature detector to take a conventional and routine measurement of forehead skin temperature.” His dissent asserted that because the relationship between arterial temperature, ambient temperature and core temperature was the natural phenomena, it could not serve as the inventive concept. He asserted that “[a]bsent a patent-ineligible law of nature, the claimed invention consists entirely of elements already combined by the prior art.”
Accordingly, Judge Hughes concluded that the district court had incorrectly “us[ed] a law of nature to supply [the] inventive concept.” “Clearly, a patent-ineligible law of nature cannot be the inventive concept that insures the claimed invention amounts to significantly more than a patent upon that law of nature.” The majority seemed to indicate otherwise.
Lessons From Exergen
Although reconciling the various decisions on eligibility may seem daunting, several factors emerge. One factor that may have helped the claims in Exergen was that they explain how the step of measuring temperature is performed with specificity: with a radiation scanner. In Rapid Litigation, the claims explained that separation was by the technique of density gradient fractionation. Contrast Ariosa, wherein the claims did not explain how the noncellular fraction was obtained, nor how to amplify the paternally inherited nucleic acid.
Also, Exergen’s claims recited a transformation of measurements into readings. Claims where something changes between the beginning and end of the claim may be more likely to be upheld than those that merely recite a series of steps as a basis for unrecited results. In Rapid Litigation, the claims described the transformation of starting material into a sample with a higher percentage of re-freezable cells. In Ariosa, the claims did not conclude with a useful result, such as identifying the father, even if that was one option under a broadly worded claim. In Exergen, the detected temperatures were transformed into the useful result of a core body temperature indication.
It is clear that Exergen will not be the last word on patent eligibility. However, as a body of case law develops, even this new area will likely become increasingly predictable.
Matthew Siegal is of counsel at Dilworth & Barrese LLP in Woodbury, New York.
The opinions expressed are those of the author(s) and do not necessarily reflect the views of the firm, its clients, or Portfolio Media Inc., or any of its or their respective affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.
 Exergen Corp. v. Kaz USA, Inc., No. 2016-2315, 2016-2341 (Fed. Cir. March 8, 2018)
 See Ariosa Diagnostics Inc. v. Sequenom Inc., 788 F.3d 1371 (Fed. Cir. 2015)
 Exergen, at *2.
 Id. at *5.
 Exergen, at *6 (citing Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 72 (2012)).
 Id. at *7.
 Id. at *8.
 Id. at*8-9.
 Rapid Litigation Mgt. Ltd. v. CellzDirect Inc., No. 2015-1570, 2016 WL 3606624 (Fed. Cir. July 5, 2016) at* 7.
 Exergen at *9.
 Id. at *10.
 Id. at *11.
 Id. at *12.
 Exergen dissent at *4.
 Id. at 6.
 Id. at 7.