Patent Law News + Insights

When Can Prior Art Invalidate an Issued Patent?

April 12, 2018

Recently, a blog reader brought a great question to our attention: If an element in a dependent claim is found in the prior art, does the whole patent fall?

As you might expect, there’s no simple yes or no answer to that question. So let’s take an in-depth look at what might happen if you discover prior art against a patent’s claims — after the patent has been issued.

The role of claims in a patent

Generally speaking, a patent is divided into a specification, drawings, and claims. (For more details, check out our blog post on the anatomy of a patent.)

Patent claims are the most important part of the document because they define the exclusive right granted to the patent owner. The rest of the patent essentially offers context — facilitating understanding of what the claimed invention entails.

Independent claims are the broadest, least restrictive claims in the patent, and do not refer back to another claim.

Conversely, dependent claims are narrower in scope than the earlier claim from which they depend, which means that you can identify them by how they explicitly refer to another claim.

What’s the problem with discovering prior art?

In a nutshell, prior art can be used to invalidate the claims in an issued patent by showing that the claimed invention is not “new” or “non-obvious.”

prior-art-patent-claims-fallDiscovering prior art against your own patent

If you discover relevant prior art before your patent has been issued, this is relatively easily resolved. You’re obliged by your duty of candor and good faith to disclose the prior art to the USPTO, and you can do this by filing an information disclosure statement (IDS). And generally speaking, you’ll have the opportunity to amend the claims of your pending application to differentiate from any newly discovered prior art.

If you discover the prior art after the patent has already been issued, there’s no obligation to cite the prior art in your issued patent. But should your competitors discover the same prior art, they could potentially use it to knock out your patent’s claims via litigation — more on that below.

Nonetheless, you have a couple of options for “cleansing” your issued patent through remedial measures provided by the USPTO: You can file a reissue application or request supplemental examination.

This post can help you to determine whether your claims might be vulnerable to invalidation in a litigation context, and whether pursuing remedial measures is the right next step.

Discovering prior art against a competitor’s patent

In a more advantageous scenario, you may have discovered prior art that’s relevant to the claims in a competitor’s patent. Could it invalidate their entire patent?

As we discuss below, that’s unlikely unless you can invalidate all of the patent’s key claims.

How patent claims could be challenged in litigation

Here we’re using the term “litigation” broadly to mean any type adversarial legal process. For example, it can be a lawsuit in federal district court, a USPTO proceeding (such as the IPR process), etc.

The validity of an issued patent can be challenged based on prior art in a litigation context on either of the following grounds (which are similar to the criteria your USPTO examiner would’ve used to assess your initial application):

  1. Section 102: Invalidity due to anticipation (or not novel). The challenger/competitor alleges that each and every element of the subjects claimed is found in one prior art reference.
  2. Section 103: Invalidity due to obviousness (or not inventive). The challenger/competitor alleges that two or more prior art references combined teach every element of the claim.

Can prior art invalidate an entire patent?

A patent as a whole is not invalidated by prior art. It’s more accurate to say that claims are invalidated by prior art.

In other words, just because one or some claims have been invalidated doesn’t mean that the entire patent is invalidated. Each claim in an application is considered to stand on its own, and is assessed separately from the others.

For this reason, the differences between independent and dependent claims could make a world of difference to a patent’s ability to withstand challenges.

Prior art and independent claims

As mentioned earlier, the independent claims are the broadest claims in a patent, with each one typically having a chain of dependent claims of narrower scope. So if an independent claim is novel and inventive, then generally all the claims that are dependent on this claim are novel and inventive. As such, it’s ideal for your independent claim to stand.

However, even if prior art knocks out an independent claim, the dependent claims may still remain valid because they’re necessarily narrower.

How? A dependent claim could include additional elements that are 1) not in the prior art and 2) not obvious in view of the prior art. This dependent claim would not be invalidated by the prior art.

That’s why robust dependent claims are critical in a patent: They provide a “fallback” position in a litigation context. If the independent claims are found to be invalid because of newly discovered prior art, the dependent claims might still be valid, enforceable, and very valuable.

Dependent claims and prior art

If a prior art reference discloses only what’s in a dependent claim (but not what’s in the independent claim), then the dependent claim typically can’t be knocked out by the prior art reference alone.

For instance, suppose an independent claim recites a widget comprising components A and B, and the dependent claim adds component C. Prior art that describes only component C wouldn’t make the claims unpatentable — unless the prior art reference also describes components A and B.

But if the prior art discloses what’s in both the independent and dependent claims, then both claims would fall.

I’ve discovered relevant prior art against an existing patent. Now what?

Whether you’ve discovered prior art against your own or a competitor’s patent, it’s best to speak to an experienced patent attorney for advice on how to handle your unique situation.

More often than not, the best thing to do is nothing at all. (How many times do you hear a lawyer say that?) But if the patent you’re looking at covers valuable technology that your company is using or might potentially use, you should definitely develop a strategy with your legal team.

At Henry Patent Law Firm, our attorneys have conducted due diligence for many patent portfolios and drafted hundreds of patent applications with meaningful claim sets. To find out how we can help you build a long-lasting patent portfolio, contact us now!

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POSTED IN: Intellectual Property, All Posts

Michael Henry

Michael Henry is a principal and the founding member of Henry Patent Law Firm PLLC. Michael specializes in creating comprehensive, growth-oriented IP strategies for early-stage companies who are developing emerging technologies.

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