February 2015 — Claim Construction-Finding of Subsidiary Facts Reviewed for Clear Error
During patent litigation, the trial court determines the scope of the patent rights by determining what the claims in the patent cover. In making this determination the trial court must ascertain the meaning of words and phrases in a process called “claim construction.” This determination is based on intrinsic evidence (i.e. what is in written in the patent or made of record during the patent application process) or extrinsic evidence (e.g. expert testimony, dictionaries, etc.). Intrinsic evidence is a matter of law whereas extrinsic evidence requires the court to make findings based on facts presented by the parties at trial, also known as “subsidiary facts”.
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