If the patentee’s invention produced unexpected results, the law says, that is pretty good evidence that it wasn’t obvious. But the law also says that if it is obvious to try to make something, and if those who might try would expect to succeed, making that thing is not patentable. It’s just the ordinary work we expect of scientists.

These two doctrines can conflict. What if it is obvious to try something, but actually trying it leads to unexpected results? This actually happens with some frequency, particularly in the chemical and pharmaceutical industries, where researchers are motivated to try various standard modifications of known chemicals but where the unpredictability of the art means that they can expect to be surprised by what they learn from time to time.

When these two legal doctrines conflict, the doctrine of unexpected results must give way. Obviousness is based on the idea that we should not give a patent if ordinary scientists could have gotten to the result without the encouragement of that patent. If researchers of ordinary skill were already motivated to try a new variation, and correctly expected that they would succeed, actually trying the new variation is normal science, not the extraordinary skill or insight required for invention. And if scientists would have created the new variation in the ordinary course of their duties, they would of necessity have stumbled upon the unexpected results. Normal science, not the incentive of a patent, led them to that course, so the invention is not patentable.

This result may alarm patent owners in the pharmaceutical industries, who have been obtaining patents for this sort of normal experimentation for years. But I think it is required by the Supreme Court’s decision in KSR, which held that an invention was not patentable if it was obvious to try. And while pharmaceutical patent owners may lament the loss of these patents, the rest of the world may not. Patents likely to be affected by the obvious-to-try rule tend to be follow-on patents used to try to extend the life of expired patents on new chemical entities, not breakthrough drugs that require strong protection.