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Centricut, LLC v. ESAB Group, Inc.: The Federal Circuit Requires Expert Testimony In Some Complex Patent Infringement Cases

Christa Brown-Sanford

Parties involved in patent infringement suits may use expert witnesses to help the judge or jury understand, and reach a verdict based upon, complex technologies and legal issues. The expert witnesses may serve to explain the facts and technologies involved by testifying about technical issues, damages, and patent law issues. In the past, parties have viewed the decision as to whether to use expert witnesses as discretionary, depending on the facts and complexity of a particular case, and in some instances would opt not to proffer testimony from an expert. However, spending the extra time and money to hire an expert may now prove necessary, or at least highly advisable, in all patent cases. This is so because in a December, 2004 ruling in Centricut, LLC v. Esab Group, Inc., 390 F.3d 1361, 1370 (Fed. Cir. 2004), the United States Court of Appeals for the Federal Circuit held that expert testimony may be required in some patent infringement cases.

Esab Group, Inc. (“Esab”) and Centricut, LLC (“Centricut”) compete in the plasma arc cutting torch market. Centricut manufactures replacement electrodes for torches, and Esab is the assignee of U.S. Patent No. 5,023,425 (the “‘425 Patent”), which claims an electrode for plasma arc torches and a method of fabricating the electrode. Centricut filed a declaratory judgment action seeking a determination that its product did not infringe the ‘425 Patent. Esab entered counterclaims alleging that Centricut infringed claims 1 and 8 of the ‘425 Patent.

The ‘425 Patent discloses a three-part electrode that comprises an emissive insert, a holder, and a sleeve positioned between the emissive insert and the holder. The point of novelty of the ‘425 Patent appears to lie in the sleeve, which is made of a material with a high work-function relative to the emissive insert. The high work-function of the sleeve improves the performance of the electrode by increasing the useful life of the electrode.

Centricut’s accused electrode comprises an emissive insert, a holder, and a ring or washer positioned between the emissive insert and the holder. The Centricut electrode significantly reduces electrode failure and has a longer useful life. Esab contended that the ring or washer of Centricut’s electrode satisfies the “sleeve” limitation of the ‘425 Patent.

In the course of a bench trial, Centricut and Esab each called fact witnesses to testify on infringement and with respect to work-function, but Centricut was the only party to introduce expert testimony. Esab relied on the testimony of the inventor, a senior staff engineer at Esab, and several employees of Centricut to support its arguments attempting to explain the longer useful life of Centricut’s product. For example, Esab argued that the useful life is a surrogate for work-function; therefore, the longer useful life was attributed to an element with a higher work-function. However, Centricut’s expert provided testimony that contradicted Esab’s arguments.

Centricut’s expert, a physics professor with a doctorate degree, testified that it was not possible to determine the relative work-functions of the sleeve and the emissive insert of the accused device without direct testing because many factors affected the work-function of a surface. Neither party introduced any evidence of tests conducted to measure directly the work-function of the materials used in the accused device. Esab only introduced test evidence concerning the accused device’s useful life.

The district court held that Centricut’s device infringed claim 1 of the ‘425 Patent by relying on work-function tables submitted by Centricut’s expert. Centricut appealed the infringement holding, and Esab cross-appealed the damages award.

The Federal Circuit reversed. Disagreeing with the district court, the Federal Circuit held that Esab had not satisfied its burden of proof on infringement in the absence of expert testimony that compared the claims as construed with the accused device. Centricut, LLC v. Esab Group, Inc., 390 F.3d 1361, 1367 (Fed. Cir. 2004). Esab presented three arguments in its efforts to prove that Centricut infringed the ‘425 Patent. However, as the Federal Circuit noted, none of the arguments were supported by expert testimony. Id. Esab first argued that because the work-function table showed the material of the ring or washer had a higher work-function than the emissive insert, it was necessarily true that the ring or washer in Centricut’s product had a higher work-function. The Federal Circuit rejected Esab’s argument, noting that Centricut’s expert testified that the work-function tables were prepared under very different conditions than a torch in operation, which greatly affected the work-function measurement. Id.

Esab’s second argument attempted to show that useful life was a surrogate for work-function. The sole testimony supporting this argument was the inventor’s testimony. The inventor, however, did not qualify as an expert on any matter under Rule 702 of the Federal Rules of Evidence because he did not study the technical subject matter in question in college, did not have a graduate degree, and did not acquire an expert knowledge during the course of employment. Centricut’s expert, on the other hand, possessed appropriate expert qualifications, and countered the inventor’s testimony explaining that a longer useful life could be attributed to different factors, including temperature, geometry of the electrode, the conductivity of the sleeve, or the sleeve’s resistance to oxidation. Id. at 1368. The expert further stated that it was not reasonable to conclude that useful life was directly attributable to work-function. Id.

Esab finally argued that the work-function limitation was satisfied in the accused device due to the emissive nature of the sleeve and insert, theorizing that emissivity and work-function were equivalent. Again, though, Esab did not use expert testimony to support this argument.

In rejecting each of Esab’s arguments, the Federal Circuit focused on the lack of expert testimony supporting Esab’s position. However, the Federal Circuit in previous decisions had seemed to acknowledge that expert testimony was neither conclusive nor necessary in a patent case. In fact, prior to this decision, the Federal Circuit had apparently been consistent in its position that expert testimony was not a per se requirement as to claim interpretation nor as to the application of claim language to accused devices. Moleculon Research Corp. v. CBS, Inc., 793 F.2d 1261, 1270 (Fed. Cir. 1986). Furthermore, when the technology in question was “easily understandable without the need for expert explanatory testimony,” the court had held that expert testimony was not necessary. Union Carbide Corp. v. American Can Co., 724 F.2d 1567, 1573 (Fed. Cir. 1984).

However, in Centricut, the Federal Circuit found that the technology in question was not easily understandable. In fact, the district court concluded that the “field of technology from which [the ‘425 Patent] sprang is so poorly understood that it qualifies as a ‘black art.’” Centricut, LLC v. Esab Group, Inc., No. Civ. 99-039-M, 2003 WL 21558348, at *7 n.6 (D.N.H. July 9. 2003).

When the technical art is complex, the Federal Circuit has repeatedly approved the use of expert testimony to establish infringement. See, e.g., Ultradent Prods., Inc. v. Life-Like Cosmetics, Inc., 127 F.3d 1065 (Fed. Cir. 1997). In fact, the court has found, presenting expert testimony to assist the fact finder may be highly advisable in some cases. Bernhardt, L.L.C. v. Collezione Europa USA, Inc., 386 F.3d 1371 (Fed. Cir. 2004). However, the Federal Circuit had not previously stated a per se rule requiring expert testimony to prove infringement in complex art areas.

Nor did the court go this far in Centricut, although it did hold, in its strongest terms yet, that based upon the particular facts of the case, expert testimony would be necessary in support of each party’s case. Accordingly, the Federal Circuit’s holding extends to cases “where the accused infringer offers expert testimony negating infringement,” and provides that “the patentee cannot satisfy its burden of proof by relying only on testimony from those who are admittedly not expert in the field.” Centricut, 390 F.3d at 1370. Therefore, it now appears that in certain instances, particularly in cases involving complex art or technologies that qualify as a “black art,” expert testimony is required to satisfy a patentee’s burden of proof if the accused infringer offers expert testimony negating infringement.

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