If you’re registering a patent, you’ll likely come upon the words “collateral estoppel.” This is a legal doctrine intended to encourage consistent rulings in cases that have identical facts. However, it’s worth noting that the rule can work against the patent owner as well with respect to rulings in the patent office. Here’s what collateral estoppel is and how to make it work in your favor.

 

What Is Collateral Estoppel?

 

In short, collateral estoppel is a rule that states that an issue that’s already been litigated can’t be litigated again. That means you can’t take civil or criminal cases to court twice. If the ruling is binding, any judge in a later case is to consider it to be true. Collateral estoppel is also important for increasing the efficiency of courts, as it prevents constant relitigation of cases.

 

For patent owners, collateral estoppel can be a double-edged sword. If you sue someone for patent infringement, they’ll likely respond by petitioning the USPTO for an inter partes review (IPR). This will determine the validity of your patent based on the infringer’s claims.

 

If the infringer wins the IPR, the USPTO will declare your patent unenforceable and your lawsuit (or part of it) will be dismissed in Federal court. If you win the IPR, the infringer won’t be able to challenge your patent on the same grounds again.

 

Patent Family Infringement

 

There are a few exceptions to the above rule. For instance, let’s say you have a family of patents and accuse someone of infringing multiple patents in that family. In this situation, the IPR decision related to one patent family member will protect another family member.

 

One precedential example of the above ruling was the Federal Circuit case involving Google and Hammond Development International with respect to whether a ruling in an inter partes proceeding in the USPTO could collaterally estop the patentability of claims in another related patent. Google LLC v. Hammond Dev. Int’l, Inc., 54 F.4th 1377 (Fed. Cir. 2022). Hammond sued Google for infringing three associated patents. Google responded by petitioning the IPR for all three patents. The resulting IPR killed two patents, but some claims of the third patent survived. Google then appealed to the USPTO concerning the decision on the third patent.

 

What turned the case around is that Hammond didn’t appeal the loss of the first two patents. As a result, the Federal Circuit decided that a claim ruled to be invalid in the first two patents prevented the claim in the third patent from being valid since the language of the claim in the third patent did not materially alter the question of patentability with respect to the claims of the first two patents.

 

Dealing With Collateral Estoppel

 

For a patent owner, the Google v. Hammond case contains two important lessons. First, if you’re pursuing patent infringement, make sure you understand how collateral estoppel works. It’s essential to recognize the ramifications of any arguments being presented, as well as how those arguments could affect the patents in your portfolio.

 

Second, appeal every single decision relevant to your case. Otherwise, you may fall into a similar trap that Hammond did and lose your patent rights on a technicality.