Patent infringement
What patent infringement actually is.
Making, using, selling, or importing something that falls within the scope of at least one of a valid patent's claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more → — without authorization. The test is element-by-element. Most accused products contain some of a claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more →'s elements; the question is whether they contain all of them.
The legal test
Two tests, both elemental
Test
Literal infringement
Every element of the patent claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → is present in the accused product or process — exactly. If a claim says "a circular surface with three magnets," the product must have a circular surface AND three magnets. Two magnets means no literal infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more → of that claim.
Test
Doctrine of equivalents
Even if a claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → element is missing literally, infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more → can still exist if the accused product has an element that performs substantially the same function in substantially the same way to achieve substantially the same result. This catches trivial workarounds — "using rubber bands instead of magnets" might not avoid infringement.
What it can cost
The three categories of damages
Lost profits.
If the patent-holder can prove they would have made specific sales but for the infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more →, they can recover those lost profits. Requires showing demand, no acceptable non-infringing alternatives, manufacturing capacity, and quantifiable profit margins.
Reasonable royalty.
If lost profits can't be proven, the court awards a royalty based on a hypothetical negotiation that would have occurred at the time infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more → began. Often expressed as a percentage of accused-product sales (1–8% is typical, higher for foundational patents).
Treble damages + attorney fees.
If the infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more → is found willful (the infringer knew of the patent and proceeded anyway without a good-faith belief of invalidity), damages can be tripled. In exceptional cases, the loser pays the winner's attorney fees.
If you receive a demand letter
The first 72 hours
- 01
Don't reply on instinct.
Anything you say can be used as evidence. Acknowledge receipt if asked, but don't admit or deny anything substantive until you've gotten advice.
- 02
Engage a patent attorney immediately.
Even if it costs $5K to evaluate, the alternative — willful infringementinfringementMaking, using, selling, or importing a patented invention without permission from the patent holder.Read more → with treble damages — costs orders of magnitude more. A formal opinion of counsel can defeat willfulness.
- 03
Get the patent number.
Look it up on PatentBrief, Google Patents, or USPTO. Read the independent claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more → slowly. Most demand letters target a specific independent claimindependent claimA claim that stands alone — doesn't reference other claims. Defines the broadest scope of the invention.Read more → — that's the one to scrutinize.
- 04
Map your product against each claim element.
Element-by-element. Where you find a missing element, you may have a defense. Where every element is present, you need a different defense (invalidity, licenselicensePermission from the patent owner to make, use, or sell the invention — usually in exchange for payment. Doesn't transfer ownership.Read more →, design-arounddesign-aroundModifying a product so it no longer falls within the claims of a competitor's patent. A core part of FTO strategy.Read more →).
- 05
Consider Inter Partes Review (IPR).
If you can find prior artprior artEarlier patents, publications, or products that existed before this patent's filing date. Patent claims must be novel over the prior art.Read more → that anticipates or makes obvious the claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more →, IPR at the PTAB invalidates ~60% of challenged claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →, costs less than litigationlitigationA lawsuit over patent infringement. Litigated patents often signal commercial importance.Read more →, and resolves faster.
PatentBrief is not a law firm. This page is general information. If you are facing a real patent dispute, work with a registered patent attorney. Failure to engage counsel can dramatically increase your exposure to damages.