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Mayo ruling by US Supreme Court on 20 March 2012

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Mayo v. Prometheus: Supreme Court rulingTimeline, context and briefs

In Mayo Collaborative Services v. Prometheus Laboratories, Inc., the US Supreme Court rejected two patents, saying that they were not on patentable subject matter. The case itself is about medical techniques, but the reasoning seems to narrow the scope for patenting software too. The court argues that the patents in question fail the "transformation" branch of the machine-or-transformation test.

The opinion was written by Justice Breyer, supported unanimously by the other Justices.

The opinion contains a detailed review of the Diehr and Flook cases and why Diehr was patentable while Flook was not.



[...] in stating that the “machine-or-transformation” test is an “important and useful clue” to patentability, we have neither said nor implied that the test trumps the “law of nature” exclusion.
Courts and judges are not institutionally well suited to making the kinds of judgments needed to distinguish among different laws of nature. And so the cases have endorsed a bright-line prohibition against patenting laws of nature, mathematical formulas and the like, which serves as a somewhat more easily administered proxy for the underlying “building-block” concern.

About Diehr

The Diehr process (held patent eligible) set forth a method for molding raw, uncured rubber into various cured, molded products. The process used a known mathematical equation, the Arrhenius equation, to determine when (depending upon the temperature inside the mold, the time the rubber had been in the mold, and the thickness of the rubber) to open the press. It consisted in effect of the steps of: (1) continuously monitoring the temperature on the inside of the mold, (2) feeding the resulting numbers into a computer, which would use the Arrhenius equation to continuously recalculate the mold-opening time, and (3) configuring the computer so that at the appropriate moment it would signal “a device” to open the press. Diehr, 450 U. S., at 177–179.

The Court pointed out that the basic mathematical equation, like a law of nature, was not patentable. But it found the overall process patent eligible because of the way the additional steps of the process integrated the equation into the process as a whole. Those steps included “installing rubber in a press, closing the mold, constantly determining the temperature of the mold, constantly recalculating the appropriate cure time through the use of the formula and a digital computer, and automatically opening the press at the proper time.” Id., at 187. It nowhere suggested that all these steps, or at least the combination of those steps, were in context obvious, already in use, or purely conventional. And so the patentees did not “seek to pre-empt the use of [the] equation,” but sought “only to foreclose from others the use of that equation in conjunction with all of the other steps in their claimed process.” Ibid. These other steps apparently added to the formula something that in terms of patent law’s objectives had significance—they transformed the process into an inventive application of the formula.

About Flook

The process in Flook (held not patentable) provided a method for adjusting “alarm limits” in the catalytic conversion of hydrocarbons. Certain operating conditions (such as temperature, pressure, and flow rates), which are continuously monitored during the conversion process, signal inefficiency or danger when they exceed certain “alarm limits.” The claimed process amounted to an improved system for updating those alarm limits through the steps of: (1) measuring the current level of the variable, e.g., the temperature; (2) using an apparently novel mathematical algorithm to calculate the current alarm limits; and (3) adjusting the system to reflect the new alarm-limit values. 437 U. S., at 585–587.

Where this case lies, between the two

Beyond picking out the relevant audience, namely those who administer doses of thiopurine drugs, the claim simply tells doctors to: (1) measure (somehow) the current level of the relevant metabolite, (2) use particular (unpatentable) laws of nature (which the claim sets forth) to calculate the current toxicity/inefficacy limits, and (3) reconsider the drug dosage in light of the law. These instructions add nothing specific to the laws of nature other than what is well-understood, routine, conventional activity, previously engaged in by those in the field. And since they are steps that must be taken in order to apply the laws in question, the effect is simply to tell doctors to apply the law some how when treating their patients.

This is interesting because it shows what we must present in order for the court to see that software ideas are just laws of nature. We have to show that writing a program or putting software on a computer is just the conventional way to use these routines. This can also be used in making the argument that software does not make a computer a new machine.


Dennis Crouch (of the Patently-O blog) says:

The result of the Mayo/Flook approach is that patent eligibility is temporally dependent. In particular, innovations that were once patent eligible will later be not eligible once the implementing-technology becomes well known.[1]

This may be what Justice Ginsburg refers to during the Alice v. CLS Bank hearing when she says:

didn't Justice Breyer say in Mayo that novelty can be relevant to patent --­­ to patent eligibility? He said there's --­­ there's an overlap.[2]

Related pages on en.swpat.org

External links

Official documents


Subsequent effects

Pre history: at the CAFC


  1. http://patentlyo.com/patent/2014/03/unpatentable-bilski-benson.html
  2. http://www.supremecourt.gov/oral_arguments/argument_transcripts/13-298_869d.pdf - page 53, line 15

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