Deere & Co. v. Bush Hog, LLC, No. 2011-1629 (Dec. 4, 2012).

A unanimous panel of the Fed Circuit reversed a grant of summary judgment of non-infringement, clarifying the limits of the “vitiation test” when applying the doctrine of equivalents.

Deere & Co’s U.S. Patent 6,052,980 covers an improvement in rotary cutters of the type that are pulled behind a tractor for large-scale mowing. The cutters often accumulate debris and can rust as a result of moisture in the debris if not cleaned properly. The patented invention reconfigures the cutters to eliminate debris traps while maintaining cutting efficiency by having front and rear portions of an upper deck wall that are placed “into engagement with, and being secured to” a lower deck wall.

The district court construed the phrase “into engagement with” as requiring direct contact between the two deck walls. Because the deck walls in the accused products do not directly contact one another, the court granted summary judgment of non-infringement based on this construction. The district court also granted summary judgment as to the doctrine of equivalents, holding that, under its claim construction, deck walls are either in contact or they are not. In the district court’s view, permitting a showing of equivalents in the absence of direct contact, would vitiate the claim language. The Fed Circuit vacated the district court’s claim construction, concluding that the claim language and specification permit engagement through indirect contact as well as direct contact. The court therefore reversed the grant of summary judgment of literal non-infringement.

In addition to the erroneous claim construction, the Fed Circuit also criticized the district court’s doctrine-of-equivalents analysis. The district court had construed “contact” to require “direct contact” and therefore concluded that allowing the upper deck wall to have indirect contact only with the lower deck wall would vitiate the court’s construction of the “direct contact” term. To this, the Fed Circuit cautioned that courts should not shortcut the equivalence inquiry by “identifying a ‘binary’ choice in which an element is either present or ‘not present.’” The vitiation test cannot be satisfied by simply noting that an element is missing from the claimed structure. By definition, the doctrine of equivalents applies where an element is literally missing. If it were otherwise, the concept of “vitiation” would swallow the doctrine of equivalents. The proper inquiry for the court is to ask whether an asserted equivalent represents an “insubstantial difference” from the claimed element or alternatively, “whether the substitute element matches the function, way, and result of the claimed element.” In the present case, “a reasonable jury could find that a small spacer connecting the upper and lower deck walls represents an insubstantial difference from direct contact.”