Walker Process Equipment, Inc. v. Food MacHinery & Chemical Corp.
The Supreme Court ruled that a company that obtains a patent by knowingly committing fraud on the Patent Office can be sued for treble damages under the antitrust laws if it then uses that patent to monopolize the market.
The decision opens a new path for competitors harmed by fraudulently obtained patents to recover triple damages, but only when they can also prove the fraud was intentional and that the patent holder actually gained illegal monopoly power.
“The far-reaching social and economic consequences of a patent, therefore, give the public a paramount interest in seeing that patent monopolies spring from backgrounds free from fraud or other inequitable conduct and that such monopolies are kept within their legitimate scope.”
Explaining why the public has a strong interest in patents being free of fraud.
How it got here: The trial court dismissed Walker's antitrust counterclaim and Food Machinery's now-moot infringement suit; the Seventh Circuit affirmed, and Walker sought Supreme Court review.
The Case in Depth
What happened
Food Machinery sued Walker Process for infringing its patent on equipment used in sewage treatment aeration systems. Walker denied infringing and counterclaimed, alleging Food Machinery had lied to the Patent Office by swearing it did not know its invention had already been in public use for over a year before applying, and that this fraudulent patent had unfairly kept Walker out of the market.
The question before the Court
If a company got its patent by lying to the Patent Office, could suing to enforce that patent count as illegal monopolization under antitrust law?
The Court's answer
Yes — the Court ruled that enforcing a patent obtained through knowing, willful fraud on the Patent Office can support an antitrust monopolization claim, opening the door to triple damages under the Clayton Act. This is a new legal path, distinct from ordinary patent-invalidity defenses, that treats deliberate fraud in getting the patent as removing the special antitrust exemption patents normally enjoy.
But proving fraud alone is not enough. The company suing must still prove all the usual elements of an illegal monopoly under the Sherman Act, including defining the relevant market and showing the patent actually gave its holder the power to hurt competition. Because those market-related facts hadn't been examined yet, the Court sent the case back so Walker could try to prove its full claim.
Curious how the Court got there? See the step-by-step legal reasoning →
Why it matters
Businesses that discover a competitor's patent was obtained through deliberate lies to the Patent Office now have a potential antitrust remedy, including triple damages, instead of just a defense to an infringement suit. Patent holders face a heightened risk from enforcing patents obtained through knowing fraud, though honest mistakes in the patent process remain protected.
What changes now
The case goes back to the trial court, where Walker will have the chance to spell out its antitrust claims more specifically, prove the alleged fraud on the Patent Office, and establish the other elements needed for a monopolization claim under the Sherman Act, including defining the relevant market and showing real harm to competition. This is a final ruling on the legal question of whether such claims can be brought at all, but the underlying factual dispute remains to be litigated.
What this does not decide
The Court did not decide that Food Machinery actually committed fraud or violated antitrust law — those remain open questions for the trial court. It also did not extend antitrust liability to patents that are merely invalid or "technically" flawed without knowing, willful fraud, and Justice Harlan's concurrence stresses that ordinary invalid or voidable patents remain outside this ruling's reach.
Concurrences and dissents
How the Justices voted
Majority (1). Justice Clark (author).
Separate writings (1). Justice Harlan (author of a concurrence).
Concurrence — Justice Harlan
“Hence, this private antitrust remedy should not be deemed available to reach § 2 monopolies carried on under a nonfraudulently procured patent.”Harlan's limit on how far the new antitrust remedy should extend.
Justice Harlan joined the majority but wrote separately to spell out precisely when this new antitrust remedy applies: only when the patent was procured by knowing, willful fraud (or enforced by someone who knew of that fraud) and all other elements of a Sherman Act monopolization claim are proven. He stressed the ruling does not cover patents that are merely invalid, obvious, or affected by unknowing 'technical fraud,' explaining that extending liability further could discourage inventors from seeking patents at all. Read the full concurrence →
How the Court got there
The legal reasoning, step by step
- The Court first addressed whether Walker's suit was really an improper attempt to annul a patent, something only the federal government can do directly. It concluded that Walker's antitrust claim under the Clayton Act was different: fraud in obtaining the patent was just one element of a broader monopolization claim, not a direct request to cancel the patent itself.
- Because patents carry a strong public interest in being free from fraud, the Court reasoned that protecting patent holders from many lawsuits does not justify blocking legitimate antitrust claims against patents obtained through deliberate deception.
- The Court then addressed what proof would be required: knowing and willful fraud on the Patent Office strips a patent holder of the usual legal exemption from antitrust liability that comes with owning a valid patent, while an honest mistake, sometimes called 'technical fraud,' provides a complete defense.
- Even after fraud is shown, the Court explained that a plaintiff must still prove the ordinary elements of illegal monopolization under the Sherman Act, including defining the relevant market for the product and showing the patent gave the defendant real power to hurt competition in that market.
- The Court rejected treating this as automatically illegal without more proof, since the general rule against automatic illegality is applied narrowly and this record lacked any examination of market effects or economic consequences.
- Because the lower courts had dismissed the case on the mistaken ground that only the government could challenge a fraudulently obtained patent, rather than for failing to plead market details, the Court found it fair to give Walker a chance to develop and prove its monopolization claim.
Doctrinal impact
Cases affected by this decision
Reaffirms Precision Instrument Mfg. Co. v. Automotive Maintenance Machinery Co. (324 U. S. 806)
Relied on as establishing that fraudulent patent procurement can be raised as a defense to an infringement suit.