Not every great discovery can become a patent. Many useful innovations, like DNA sequences, simply cannot be patented, because they are natural phenomena. Yet others may be rejected because they are anticipated by previous inventions or for other reasons recognized by law. On the other hand, countless famously terrible ideas, like the sheep treadmill and jet-powered surfboard, actually were patented.

To be patentable an invention must satisfy several requirements. One of the most significant is that the invention cannot be obvious in light of existing inventions. This requirement is so important that even an issued patent can be found invalid (hence unenforceable) if the invention is deemed obvious.

Naturally, many people accused of patent infringement contend that the asserted invention was obvious. Anyone making this argument must first show that all elements of the patented invention were present in existing inventions, and second point to a motivation to combine those elements.

The second part of the obviousness test requires that the challenger show that someone skilled in the art would have been motivated to combine the prior-art references to produce the claimed invention with a reasonable expectation of success. In other words, the accused infringer must explain that this hypothetical skilled person would have recognized elements of the asserted invention in prior references and been motivated to combine them to create the same invention.

Although this test is at least a decade old, its second part (why someone would have been motivated to make the combination) is often overlooked. As an example of an insufficient obviousness defense, if I was arguing that the jet-powered surfboard was obvious, I might point out that surfboards already existed, and jet engines already existed, therefore a jet-powered surfboard is an obvious combination. Notice how I left out any explanation of why those existing parts would have been combined? Skipping that last step is not allowed.

On occasion even judges forget the “why” portion of the test and need to be reminded that a full explanation of the motivation to combine is required. That is exactly what happened in Personal Web Technologies, LLC v. Apple, Inc. Personal Web accused Apple of infringement and Apple defended itself by arguing that Personal Web’s data processing patent was obvious. The administrative judges on the Patent Trial and Appeal Board agreed with Apple and found the patent was just a combination of two earlier inventions.

Personal Web argued to the Federal Circuit, the court that hears all appeals from patent lawsuits, that the PTAB judges failed to apply the correct test. The court agreed, holding that the PTAB (1) did not show that each element of Personal Web’s patent claims were taught by prior-art references, and (2) did not explain the motivation to combine the two earlier inventions. The court instructed the PTAB to apply the test again, this time correctly. Unless the PTAB, upon reapplying the test, insists that the two prior inventions would have been obvious to combine, Personal Web’s patent will be alive again!

The Federal Circuit did not make any new law; it just reaffirmed what the correct law is. The court said that the amount of evidence that the PTAB must muster to support a motivation-to-combine might differ depending on the complexity of the technology or of the cited references.

While not as attention-grabbing as deciding a new legal issue, the case is an important reminder that all courts must uniformly apply the correct standard for establishing obviousness. Without occasional reminders like this, the next jet-powered surfboard might never receive patent protection, and what kind of world would that be?