Ex-Post-Facto obviousness

One of the major dangers when assessing the obviousness of an invention is the experience and knowledge of the court, i.e., the Judge or jury will see the invention in hindsight, impacting its assessment of validity. Very many good inventions seem obvious with the benefit of hindsight.

A key factor in this problem is that patents take often 3-5 years to issue, and indeed are rarely in court within a decade of filing – however, whether the invention claimed in a patent is obvious must be assessed in light of the state of the art as of the Priority Date for that patent. It is easy for a court to fall into the trap of thinking a patent is obvious because of its knowledge of the post-invention world and this mistake is known as Ex-Post-Facto Obviousness or the ‘Hindsight Problem.’

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