Diamond v. Diehr ruling by US Supreme Court on 3 March 1981
Diamond v. Diehr, 450 U.S. 175, 192 (1981) is one of the very few cases where the Supreme Court of the USA ruled on the definition of patentable subject matter. The court upheld a patent on a way to use rubber-curing machinery, controlled by a computer.
At issue in this case is a system for curing rubber with a rubber-curing machine aided by a computer, using specific mathematical formulas. The Supreme Court upheld the patent. The ruling did not directly address the subject of patenting software ideas, but it was used by the lower courts to justify broadening the scope for the patenting of software.
 The opinion
The opinion was written by Justice William Rehnquist. It was a 5-4 decision, and the dissenting opinion was written by Justice Stevens, joined by Justice Brennan, Justice Marshall, and Justice Blackmun.
The ruling also confirms that "excluded from such patent protection are ... abstract ideas.".
insignificant postsolution activity will not transform [450 U.S. 175, 192] an unpatentable principle into a patentable process. Ibid. 14 To hold otherwise would allow a competent draftsman to evade the recognized limitations on the type of subject matter eligible for patent protection. On the other hand, when a claim containing a mathematical formula implements or applies that formula in a structure or process which, when considered as a whole, is performing a function which the patent laws were designed to protect (e. g., transforming or reducing an article to a different state or thing), then the claim satisfies the requirements of 101. Because we do not view respondents' claims as an attempt to patent a mathematical formula, but rather to be drawn to an industrial process [450 U.S. 175, 193] for the molding of rubber products, we affirm the judgment of the Court of Customs and Patent Appeals.
Note that the "whole" is an algorithm plus a structure/process which, for example, transforms an article to a different state or thing. It's not a mathematical patent, it's a rubber curing patent. However, the US CAFC has used the "as a whole" doctrine to allow pure software patents which include no such transformation.
 Amicus briefs
Briefs of amici curiae urging affirmance were filed by:
- American Patent Law Association, Inc. (authors: Donald R. Dunner, Kenneth E. Kuffner, and Travis Gordon White)
- Applied Data Research, Inc. (Read the brief) (author: Morton C. Jacobs) - which used the Cabinet for the blind example
- Chevron Research Co. (authors: William L. Mathis and Harold D. Messner)
- Los Angeles Patent Law Association (authors: Reed C. Lawlor and James W. Geriak)
A brief of amicus curiae urging reversal was filed by:
- National Semiconductor Corp. (authors: Edward S. Irons, Mary Helen Sears, and Robert P. Beshar)
 Related pages on en.swpat.org
- Mentioned in the introduction of the court's decision
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