The Use of Prosecution History for Claim Construction in Canada and the United Kingdom: Is a Patent a Journey or a Destination?
Author(s): William J. Murphy
In the last few years, two Federal Court cases have qualified the doctrine of “file wrapper estoppel” to allow prosecution history to be used in the construction of granted patent claims. A third case, while acknowledging that “Canadian law appears quite settled that extrinsic evidence is not relevant to claim construction,” raises the question whether it is time to revisit the rule against using such evidence in claim construction. This article considers Canadian and UK approaches to this issue and argues that the use of file wrapper estoppel remains neither correct nor desirable in Canada.