Festo fog

From Mark R. Hull, Festo: A Fog Between the Bars, 37 Akron L. Rev. 339 (2004):

The Supreme Court's rejection of the Federal Circuit's complete bar rule has been viewed by many as a triumph for the patent system. n131 Some commentators have, however, taken a far less enthusiastic view of the Supreme Court's new rebuttable presumption rule. n132 Of concern is that the Court's approach appears to be a new, never before used creation n133 for which the Court provides scant guidance on its proper application. n134 As a result, a substantial number of unanswered [p. 365] questions make it difficult to understand Festo's true impact. n135

(...)
the Federal Circuit could echo Bernard Witkin's famous quote, "on a clear day, you can foresee forever," by taking a broad view of foreseeability. n142 A broad view could result in patentees' inability to claim any equivalents, or, at most, only equivalents in a rapidly developing field. n143

(...)
The amicus curiae brief from the Institute of Electrical and Electronics Engineers has been suggested as the source for the Court's [*368] use of foreseeability. n144 The brief, however, proposed a "foreseeable bar' that focused on the foreseeability of the effect of an amendment, which differs somewhat from the foreseeable equivalent test specified in Festo. n145 A discussion of foreseeability that is closer to the Festo test can be found in two recent Federal Circuit opinions. n146

Some of the footnotes:

n131. See Lawrence B. Ebert, Supreme Court Festo; Equivalents Still
Limited, Intell. Prop. Today, July, 2002, at 10. (indicating that the popular press believe the Supreme Court's Festo decision to be a victory for inventors over copyists); See e.g. Ron Cahill, Festo Restores Right Economic Incentives, U.S. Supreme Court Affirms Worth of Existing Patent, Companies, 168 N.J.L.J. 1225
(2002) (stating that the Supreme Court decision "restored the right
economic incentives," and will encourage competitions to invest in creating innovative advances in technology rather than making insubstantial changes to patented technology in order to avoid infringement); Jennifer Miller, Festo: Blessing to
Patent Holders or Thorn in Their Sides?, 2002 Duke L. & Tech. Rev. 17, 18 (2002) ...

n133. See Lawrence B. Ebert, It's a Strange, Strange World, Intell.
Prop. Today, October 2002, at 46 (indicating that the tests enunciated by the Court bear no citation to previous legal authority and appear to have never been used). See also supra note 115 (indicating that the source of the rebuttable
presumption was the amicus curiae brief from the United States); Brief for the United States as Amicus Curiae Supporting Vacatur and Remand, Festo Corporation v. Shoketsu Kinzoku Kogyo Kabushiki Co., 2001 WL 1025650 (2001) (No. 00-1543)

n134. See Ebert, supra note 133 (stating that the Supreme Court
provided no footnotes as to the origins of the three situations it articulated); Lawrence B. Ebert, Litera Scripta Manet?, Intell. Prop. Today, August 2002, at n.2

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An issue now is that the tangential prong of Festo begins to resemble the old Hughes-I flexible bar. Just remember: no extrinsic evidence for the tangential prong, so say something (short) about why you're amending.