Technology Law Source : Technology Lawyers & Attorneys for Patents, Trademarks & Copyright Issues in Ohio, Washington DC, Florida

Ensnarement is a powerful defense in any patent case where the doctrine of equivalents is at issue.  It's time for defendants to "discover" this under-utilized defense.    Despite litigating numerous doctrine of equivalents cases, I've only litigated one case where an ensnarement defense was vigorously asserted.

Ensnarement, seminally set forth in Wilson Sporting Goods, prevents a patentee from claiming a range of equivalents that "ensnares" the prior art.  To make that determination, the original claim is redrafted as a hypothetical claim by replacing certain claim terms with the asserted equivalents.  As a result, the hypothetical claim literally encompasses the claimed product.  In DePuy v. Medtronic, e.g., the claim term "spherically-shaped portion" was replaced with "conically-shaped portion" in the hypothetical claim because the accused product included a conically-shaped portion.  The relevant question is then whether the hypothetical claim is allowable over the asserted prior art.  If the hypothetical claim is not allowable, then there is no infringement because the asserted range of equivalents "ensnares" the prior art.

Two features of ensnarement make the defense particularly powerful.   First, ensnarement is a question of law.   In DePuy, the district court held a separate bench trial on the issue of ensnarement after the jury trial (See DePuy, 526 F.Supp.2d 126).  The Federal Circuit affirmed the propriety of the court's ensnarement proceeding, holding that ensnarement is a question of law like any other limitation on the doctrine of equivalents.  Second, the defendant merely bears the burden of producing prior art to challenge the hypothetical claim; the patentee bears the burden of establishing that the hypothetical claim is patentable.  This is in stark contrast to the clear and convincing standard  that a defendant must meet to establish invalidity. 

Ensnarement, then, effectively allows a defendant two chances to win with its invalidity arguments.  A defendant should request a "DePuy Hearing" after the trial if there is a finding of infringement under the doctrine of equivalents.  At that hearing, defendant can re-raise its same basic invalidity arguments because ensnarement and invalidity have significantly different burdens and ask different questions (patentability of the hypothetical claim vs. validity of the original claim).  The second bite at the apple could prove invaluable.  As an example, a court is unlikely to grant defendant's JMOL on anticipation or obviousness if the question is close.  With an ensnarement defense, though, the "close call" should go to the defendant, and "close calls," of course, are far easier to assert post-KSR.  Further, from the Court's perspective, a finding of ensnarement may be a better option because it is more likely to withstand appeal than a grant of JMOL on a jury verdict of validity.  From a defendant's perspective, whether the patent is invalid or the prior art ensnared is typically of no significant consequence.  Thus, in any case where infringement is based on the doctrine of equivalents, defendant should assert an ensnarement defense and request a "DePuy Hearing" on the issue.

• Email This
• Print
• Share Link

A decision issued by the Federal Circuit April 29, 2011 offers a lesson for patent prosecutors to talk to each named inventor about what they consider to be the best way of practicing their invention.  Though anti-intuitive, it is possible to have multiple best modes. In Wellman, Inc. v. Eastman Chemical Co. (Fed. Cir. 2011), the Federal Circuit has held that the best mode requirement of 35 U.S.C §112 applies to each named inventor (as opposed the inventors collectively).  The statutory language on this point is less then clear as §112 requires disclosure of the best mode "contemplated by the inventor."  The issue is whether "the inventor" refers to a single best mode contemplated by all the named inventors or whether "the inventor" refers to each and every inventor, thereby allowing for the possibility of multiple best modes for a patent.  In addition, the term "best mode" suggests only one mode per patent.   Up to this point, Federal Circuit precedent was also unclear on the issue.  The only Federal Circuit decision addressing this issue supported the latter position, but did so in dicta in a footnote.  See Pannu v. Iolab Corp., 155 F.3d 1344, 1351 n.5 (Fed. Cir. 1998).   However, multiple Federal Circuit decisions have used loose language that supports the former position, though those decisions weren't presented squarely with the issue.

In Eastman, the Federal Circuit adopted the dicta in Pannu and held that "best mode issues can arise if any inventor fails to disclose the best mode known to him or her."  In Eastman, one of the inventors had testified that a certain recipe for PET resins was, in his mind, the best resin available at the time the application was filed.  The patentees, however, choose to maintain that recipe as a trade secret rather than specifically disclose it in the patent application.  Instead, the patent "hides" the best mode by disclosing broad ranges for certain elements that technically encompass the best mode recipe, but which failed to enable a person of ordinary skill to practice the best mode.  Significantly, the patent actually "leads away" from one critical element through statements about "typical" and "preferred" properties within a range that the actual best mode compound does not have.

The lesson of Eastman for patent prosecutors is to talk to each named inventor about what they consider to be the best way of practicing their invention.  Though anti-intuitive, it is possible to have multiple best modes.  Further, if you're dealing with a chemical patent, it's much safer to directly disclose the actual best mode, but if you opt to use "ranges" to make the required disclosure, the best mode must be enabled.

Two final comments.  First, Chief Judge Radar found that "Wellman intentionally concealed the best mode."  Perhaps we will find out if intentional concealment of the best mode is a sufficient predicate for an inequitable conduct defense.  Second, Patent Reform (addressed in this post), removes the best mode requirement from 35 U.S.C § 112.  So, it's possible that this may be the last significant best mode decision.

• Email This
• Print
• Share Link