What Is Patent Infringement

Rich Goldstein

Founder & Principal Patent Attorney

A patent gives the patent holder the legal intellectual property right to exclude others from making, using, selling, or importing whatever is within the scope of the patent. Patent infringement is when someone carries out an act that infringes on this legal right without the permission of the patent holder. 

Deciding what constitutes a patent infringement and the type of patent infringement that may have taken place can get complicated. If you discover someone is somehow using or selling your patented invention without your permission, you can pursue litigation against them in the United States federal court. 

What Is Patent Infringement?

Typewriter with a finished copy of the term Copyright Claim

Patent infringement is essentially the violation of a patent owner’s rights with respect to a specific invention for which there is a valid patent. Someone commits patent infringement by making, using, selling, or important whatever is within the scope of the patent without the patent owner’s direct permission to do so.

Types of Patent Infringement

There are a number of different types of patent infringement.  This means there are multiple manners and ways in which someone can be infringing on your patented invention, and ways you can bring action against them in court. 

Direct Infringement

Direct infringement is the most obvious type of patent infringement, and probably what comes to mind first. According to 35 U.S.C. § 271, Direct infringement occurs when some individual or entity offers to sell or sells within the United States or imports into the United States a component of a patented machine, manufacture, combination or composition, or a material or apparatus for use in practicing a patented process, constituting a material part of the invention, knowing the same to be especially made or specially adapted for use in an infringement of such patent.

Essentially, direct infringement is actively engaging in a prohibited use of someone else’s patented property. For example, if someone is selling a product that is identical to yours, this would be direct patent infringement. 

Indirect Infringement 

Indirect infringement of a patent occurs when some individual or entity causes or assists another individual or entity to infringe on patented property. This infringement must infringe on at least one material aspect of the patent. 

There are two different types of indirect patent infringement: induced infringement and contributory infringement. 

Induced Infringement

Inducing infringement is actively inducing another person or entity to make prohibited use of someone else’s patent. For example, if an entity actively provides the manufacturing blueprints of a patented product to another entity, this would be indirect patent infringement. 

Contributory Infringement

Contributory infringement occurs when a person or entity knowingly provides a product or component of a product or service that helps the recipient directly infringe on a patent.  Also, the provided product or component must not have a substantial non-infringing use. 

Basically, a person or entity must: 

  1. Know of the patent; and
  2. Know that his or her actions would lead to infringement of the patent.

How to Prove Patent Infringement

If you think your patented invention may have been infringed, you can bring a patent infringement lawsuit as the patent holder.  This legal action is brought in United States federal court, not in state court or in front of the United States Patent Office. 

To prove patent infringement in court, you must meet the following three elements:

  1. You own a valid patent;
  2. The alleged infringer has engaged in an act of infringement; and
  3. The infringing product or process incorporates all the material features of at least one independent patent claim.

Patent Ownership and Validity

As an initial matter, you must prove that you are the owner of a valid patent. This breaks down into two parts: ownership and validity. 

Opposing inventors fighting over a product's patent infringement

Ownership of a patent can typically be proven with a written assignment of the patent to you. This could be official documents from the United States Patent and Trademark Office approving your patent.  It could also be a contract assigning to you the ownership rights of a patent.

Proving the validity of a patent is often where the fight can take place. This is because this is the place the defendant (i.e., the infringing party that you are suing) will try to refute your argument. 

There are numerous ways a patent could be determined invalid by a court:

  • Information was withheld from the patent application;
  • Information in the patent application was false or misleading; 
  • Written description of the patent is insufficient;
  • One or more of the claims is obvious or contemplated in prior art. 

As you can see from the last one, this means your patent infringement lawsuit may entail a renewed review of all of the prior art related to your patent. 

To determine whether these elements are met, a court will compare each element of your applicable patent claim to the elements of the defendant’s product or process.

Infringement on Your Patent

Second, the patent holder must prove one of the types of patent infringement on the patented invention: direct or indirect, and within indirect, either induced or contributory. 

The easiest way to prove this is with evidence of the competing product or invention so that it can be compared with the patent side to side. If you have an indirect infringement claim, then you will ideally have some documentary evidence of directing or assisting in the infringement, perhaps in emails or letters.  

Prove Violation of a Specific Patent Claim

More than just comparing the patented invention and infringing invention, you as the patent holder will need to prove that the competing invention infringes on a specific claim that is contained within your patent. This means you will need to conduct a detailed claims analysis and will need to refute the claims analysis completed by the defendant. 

This claims analysis is often completed by an expert in the field that your patent is in. It will break down each patent claim in your application, argue for its validity, and then compare it to the defendant’s competing invention. 

It is helpful to break down each element of every claim of your patented invention into a claim chart and compare those elements to the defendant’s invention elements in a side by side manner. 

Doctrine of Equivalents

The doctrine of equivalents is a legal doctrine that can come into play in patent lawsuits.  The doctrine of equivalents allows for a finding of patent infringement for a patented invention even if an infringing invention does not fall within the literal scope of the infringed invention, but is nevertheless equivalent to the infringed invention. 

Drafting a patent infringement complaint

To use the doctrine of equivalents, the competing invention must:

  1. Performs substantially the same function as the infringed invention;
  2. In substantially the same manner; 
  3. To achieve the same result. 

The doctrine of equivalents will also apply if two elements of the competing product or invention are interchangeable and a person with ordinary skill in the same field would have known that the elements were interchangeable when then infringement occurred. 

Limitation of the Doctrine of Equivalents

There are limitations to the doctrine of equivalents. This doctrine must be applied to the individual elements of a patent claim rather than to the patent as a whole. 

The patent holder must prove that the infringing claim was not foreseeable to someone of ordinary skill in the same field. This foreseeability element is interpreted broadly by the court.  The courts have found that an equivalent is foreseeable if someone in the field would have known the equivalent existed, even if the suitability of that equivalent as an alternative was unknown. 

Another limitation on the doctrine is that if a patent discloses an alternative way to create a product or invention but does not specifically claim it within that patent, then that alternative way is not covered by the patent’s protection and can be used freely by the public. 

This is why it can be very important not only to draft a patent application that explains your product or invention in detail but to also make sure you make as many claims as possible related to your invention. 

Consequences of Patent Infringement

If you win your patent infringement lawsuit in court, you will be able to get an award of damages from the infringer for the infringement on your patented invention.  

One form of damages is some type of royalty payment for infringing on your product. This means the infringing party would still be able to market the competing invention but would have to pay you a percentage of any profit. 

If you are able to prove it, you may also be able to recover “lost profits”. These are the profits that you lost because of the competing product. They can be more difficult to prove because they are often viewed as speculative by the court. 

Old copy of a pending patent

 Another potential remedy for patent infringement is to get an injunction against the infringer.  This would prevent the infringing party from continuing to make and market the competing invention. This is typically viewed by the court as a more extreme remedy and is typically avoided except in more unique circumstances where it may be justified.

Patent Infringement if Patent Pending

If your patent is patent pending with the Patent Office, you typically cannot pursue patent infringement litigation against a potentially infringing party. This is because you must have a valid patent in order to establish patent infringement, as explained above. 

Ideally, your patent pending status alone will provide “psychological protection” that deters competitors from making and selling competing inventions.  That is, not knowing if and when your patent will issue, it is hard for competitors to launch potentially infringing products.  They could spend a fortune gearing up to produce their copy, only to have your patent issue and have to immediately stop.  Also – while you cannot pursue formal litigation in court, you can engage patent attorneys to draft well reasoned letters to the potentially infringing party.  

These letters and resulting discussions should point out how the product or invention will infringe on your pending patent and why the infringing party will likely be confronted with litigation in the future. 

Drafting Patents That Are Enforceable

Given the expense and headache of litigation, you can see from this discussion that it can be vital to draft your patent claims in a manner that will make them enforceable possible down the line. A poorly written patent will leave many options for others to avoid infringement and may be found to be invalid once scrutinized in court.

Thoroughly Search for Prior Art

The most important way to ensure your patent claim will withstand scrutiny down the line in potential patent litigation is to make sure you have thoroughly researched and refuted all prior art.  

Prior art is typically where defendants have luck in defeating a patent infringement claim, and where courts are more willing to find ambiguity in favor of the defendant. If you find all of the closest prior art and bring it to the attention of the Patent Office during patent prosecution, no one will be surprised by it if you later need to litigate your patent. This means thorough and exhaustive prior art searches are integral during the patent prosecution process.  These should be completed by you as well as an experienced patent attorney. 

Construct Well Written Claims

Another important way to fight against infringement upfront is to draft well-written claims in your patent application. The claims in your patent should have reasonably broad independent claims.  Each of these independent claims should have a series of cascading detailed and narrower dependent claims associated with them. 

This is why it is critical to engage an experienced patent attorney to assist you in drafting claims that will stand up to potential scrutiny later on should your patent end up in court. 


If you think a competing product or invention may be infringing on your patent, you can pursue litigation in federal court with a patent infringement claim.  Make sure you own a valid patent and make sure one of the forms of patent infringement has been met.  You may be able to pursue litigation against multiple parties if you find there have been some contributory or induced infringement. 

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