Prior Art in the District Court

This article is an empirical study of the evidence district courts rely upon when invalidating patents. To construct our dataset, we collected every district court ruling, verdict form, and opinion (whether reported or unreported) invalidating a patent claim over a six-and-a-half-year period. We then coded individual invalidation events based on the prior art supporting the court’s analysis. In the end, we observed 3,320 invalidation events based on 817 distinct prior art references. The nature of the prior art relied upon to invalidate patents informs the value of district court litigation as an error correction tool. The public interest in revoking erroneous patent grants depends significantly on the reason those grants were undeserved. Distinguishing between revocations that incentivize future inventors and those that do not requires understanding the reason individual patents are invalidated. While prior studies have explored patent invalidity in general, no study has reported data at the level of detail necessary to address these questions. The conclusions here are mixed. On one hand, invalidations for lack of novelty bear many indicia of publicly beneficial error correction. Anticipation based on obscure prior art appears to be quite rare. When it comes to obviousness, however, a significant number of invalidations rely on prior art that would have been difficult or impossible to find at the time of invention. This complicates — though does not necessarily refute — the traditional view that obviousness challenges ought to be proactively encouraged