Stumbo v. Eastman Outdoors, Inc.
508 F.3d 1358 (2007)
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Rule of Law:
To defeat summary judgment on a claim of patent infringement under the doctrine of equivalents, the patentee must provide particularized testimony and linking argument showing the insubstantiality of the differences between the patented invention and the accused device, specifically as to the function-way-result test.
Facts:
- Steve Stumbo invented and obtained U.S. Patent No. 5,628,338 for a portable, collapsible hunting blind.
- Stumbo's patent claims a 'closable vertical opening' located along a side edge or vertical corner to allow for ingress and egress.
- The patent specification states that the blind's support leg members 'must flex in order to enable the door opening to expand for ingress and egress.'
- Eastman Outdoors, Inc. and Ameristep Corporation (Defendants) manufactured and sold portable, collapsible hunting blinds.
- The Eastman Outdoors blind features a triangular-shaped 'loose door flap' created by a zipper running diagonally from the bottom-center to the top-center of a side wall.
- The Ameristep blind features a triangular door opening created by two zippers that meet in the center of a side wall.
- Entry and exit through the Defendants' blinds do not require the structural support members to flex.
Procedural Posture:
- Steve Stumbo filed a patent infringement lawsuit against Eastman Outdoors, Inc. and Ameristep Corporation in the U.S. District Court for the District of Colorado.
- The Defendants moved for summary judgment, arguing their products did not infringe Stumbo's patent.
- The district court first construed the patent claim term 'closable vertical opening' to mean a 'slit-like opening that runs straight up and down'.
- The district court granted summary judgment in favor of the Defendants, finding no literal infringement and no infringement under the doctrine of equivalents.
- Stumbo (appellant) appealed the district court's summary judgment rulings to the U.S. Court of Appeals for the Federal Circuit.
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Issue:
Do the accused hunting blinds, which feature triangular door openings that do not require the blind's support structure to flex for entry, infringe a patent claiming a 'closable vertical opening' that requires its support structure to flex, under the doctrine of equivalents?
Opinions:
Majority - Moore, J.
No. The accused hunting blinds do not infringe the patent under the doctrine of equivalents because their triangular door openings do not function in substantially the same way or produce substantially the same result as the patented vertical slit opening. First, the court affirmed the district court's claim construction of 'closable vertical opening' as a 'slit-like opening that runs straight up and down,' based on the claim language and the specification. This construction precludes any finding of literal infringement. Second, under the doctrine of equivalents, the court applied the function-way-result test. The 'way' the openings operate is substantially different: the patented slit requires the blind's leg members to flex to allow entry, whereas the accused triangular flaps do not. The 'result' is also different, as the Defendants provided evidence that their wider, triangular openings are safer and easier for hunters with equipment to use. Stumbo failed to rebut this evidence with the required 'particularized testimony and linking argument,' instead offering only conclusory expert declarations that the openings were 'substantially equivalent.' Such cursory statements are insufficient to create a genuine issue of material fact and cannot survive a motion for summary judgment.
Analysis:
This decision reinforces the high evidentiary bar for patent owners seeking to prove infringement under the doctrine of equivalents at the summary judgment stage. The court's emphasis on 'particularized testimony and linking argument' serves as a clear warning that conclusory expert opinions are insufficient to survive summary judgment. Furthermore, the case illustrates how a narrow claim construction, derived from specific limitations in the patent's specification (like the 'legs must flex' language), can effectively foreclose not only literal infringement but also infringement under the doctrine of equivalents. This outcome highlights the critical interplay between claim construction and the subsequent infringement analysis, showing that the former often determines the outcome of the latter.
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