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Causal Responsibility and Patent Infringement

Posted by on Tuesday, March 21, 2017 in Articles, Volume 70, Volume 70, Number 2.

Causal Responsibility and Patent Infringement


It is not uncommon for multiple parties in the stream of commerce—manufacturers, distributors, end users—to be involved in the infringement of a single patent. Yet courts continue to struggle with such scenarios. Attempts to deal with them—particularly when plaintiffs asserted so-called method patents, which cover specific “steps,” or actions—have produced results that defy commonsense notions of legal responsibility. In method patent cases, the patentee must clear much higher legal hurdles to prevail against a manufacturer who designed and supplied an infringing device than against an end user who simply bought that device and operated it as intended. The manufacturer can lose only upon proof of fault, while the user is subject to strict liability—a result that seems backwards because the manufacturer is clearly the more responsible party. Even greater difficulties arise when the manufacturer performs some steps of a method patent and the user performs the others, giving rise to a so-called “divided infringement” problem. One such case, Akamai v. Limelight, has been in litigation for over ten years and generated multiple appellate opinions, including a decision by the Supreme Court. Although the Court of Appeals for the Federal Circuit finally resolved Akamai in a fact-specific fashion, no comprehensive solution to the divided infringement problem is in sight.

I explain that these problems persist because patent law formalistically clings to what I term the “performer/non-performer distinction,” which holds that physical performance of an act is the linchpin of legal accountability. I then contend that they can be solved by reading the Patent Act in view of the principle of causal responsibility, which pervades the law and rests on a firm philosophical foundation. Simply put, this principle holds that one is responsible for the actions of others that one has caused, leading to the legal effect of imputing the act of the “causee” (in patent cases, often the user) to the causer (e.g., the manufacturer). I draw on examples from criminal law and tort law to elucidate this principle and demonstrate its consistency with the Patent Act. I also maintain that applying causal responsibility in patent law would lead to three practical and sensible results. First, doing so would effectively lower the mens rea barriers needed to establish the liability of manufacturers who supply devices configured so that their only intended use by a passive customer results in the performance of steps of some method patent. Second, it would provide a path for resolving the vexing problem of divided infringement exemplified by Akamai. Third, the proposed approach may in some cases help to shift the burden of ensuring compliance with existing patents from end users to manufacturers, which is as it should be.


Associate Professor, George Washington University Law School.