The claims are the legally operative part of a patent for infringement purposes.  That is, if an accused device contains all of the literal elements of a patent claim or equivalents thereof, the device infringes that claim.  Patent claims have two parts:  the preamble (e.g., “a seating apparatus comprising:”) and the body (e.g., “a plurality of legs; a seat; and a back”). 

Usually an infringement analysis involves only the elements in the body of a claim.  But sometimes, depending on the relationship between the preamble and the body, the terms in the claim preamble are considered in infringement.  Whether elements in a preamble should be part of the infringement analysis can be a hotly contested, and dispositive, question in patent litigation.

That was the case in a currently pending lawsuit in New York federal court between retired professor and LED innovator Gertrude Neumark Rothschild and Durham, North Carolina LED maker Cree, Inc. (Cree).  In a recent decision (opinion.pdf), Judge William C. Conner denied Cree’s motion for summary judgment that it did not infringe one of Rothschild’s patents because the court determined that the preamble of an asserted patent claim should not be part of the infringement analysis.

In 2005, Rothschild sued Cree for patent infringement, alleging that its methods of producing gallium nitride and aluminum gallium nitride LEDs infringed two of her patents.  U.S. Patent Nos. 4,904,618 (‘618 patent) and 5,252,499 (‘499 patent) are directed to methods of making LEDs capable of emitting short wavelength (green or blue) light. 

The patents address the problem of “doping” wide band gap semiconductor materials, an essential step in creating adequate conductance for the materials to function as LEDs.  Doping means adding impurities to a semiconductor to increase the number of free charge carriers. 

The preamble of claim 10, the only asserted independent claim of the ‘499 patent, claimed a “method of forming a low resistivity semiconductor from a wide-gap semiconductor substrate that has a tendency to become compensated when it is doped, comprising…”  Cree tried to dispose of the ‘499 patent by a summary judgment motion in which it argued that this preamble should be part of the infringement analysis, and that its accused production process does not infringe the patent because it does not include the elements of the preamble.

Cree also contended that Rothschild waived her right to raise the issue of excluding the preamble from the infringement analysis because she failed to make that argument earlier in the case, and, in particular, remained silent about it during the court’s claim construction proceedings (Rothschild even offered constructions for terms appearing only in the preamble).  The court disagreed, noting a lack of precedent on such waivers and that depriving Rothschild of the argument would cause her substantial prejudice, likely destroying her infringement claim against Cree.

Generally, a claim’s preamble becomes part of the infringement analysis (i.e., the preamble is “limiting”) if it recites essential features of the invention.  Stated another way, if the body of the claim recites a structurally complete invention, the preamble is not necessary for a determination of infringement.

Judge Conner found that the body of claim 10 adequately describes a complete process and that reference to the preamble is not necessary to supply any missing steps or make the claim body comprehensible.  Rather, he found that the preamble merely specifies a desirable result achieved by the process recited in the body of the claim, i.e., formation of a low-resisitivity semiconductor from a wide-gap semiconductor substrate.

Accordingly, the court held that the preamble was not part of the infringement analysis.  Because Cree’s non-infringement arguments hinged on elements of the preamble, the court denied the motion for summary judgment.  Now the case will go forward to trial, or, if recent history is any guide, Cree will settle and take a license from Rothschild. 

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