Warner-Jenkinson Company v. Hilton Davis Chemical Co. (901422128)

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Read for 3/28/11

Reading Notes

  • Decided by the USSC in 1997
  • Hilton sued Warner for infringement of a 1985 patent for purifying dyes
    • Patent specifies filtration through a porous membrane at pH of 5-9
      • This was specified because examiner found an overlap with an old patent which was above pH 9
  • Hilton sued based on doctrine of equivalents
    • District court ruled in Hilton's favor
  • Court rejects Warner's argument that the doctrine is inconsistent with the Act of 1952
    • USSC disagrees
    • Court in concerned that the broad application conflicts with holdings that a patent may not be enlarged beyond the scope of its claims
      • To avoid this, apply doctrine individually to each element and not the product/process as a whole
  • Warner is wrong to suggest that surrender of subject matter during the patent prosecution establishes a bright line beyond which no equivalents may be claimed
    • Must determine the reason behind the language change
      • In this case it is known why the upper limit was added but not the lower
  • USSC reverses and remands
    • Federal Circuit did not consider all requirements of the doctrine
  • USSC does not speak the death of the doctrine but does seek to clarify it
  • Parties disagree about why the low limit (pH 6) was added
  • Jury ruled infringement under the doctrine but awarded only 20% of the damages for lack of intent
    • CAFC affirmed
  • Warner argues doctrine is inconsistent with aspects of the Act of 1952
    • Section 112 - specific claims
    • Section 251-252 - reissue process
    • None of these hold enough water
  • USSC is concerned the doctrine has become unbounded by patent claims
    • Must be applied to individual elements and not the invention as a whole
  • Warner also offered alternative arguments for a more restricted doctrine of equivalents
    • Graver Tank never meant to supersede a well-established limit on non-literal infringement
    • Any surrender, during prosecution, for whatever reason, precludes recapturing subject matter
      • Only if it is to avoid unpatentability does it do this
  • Since the reason for the lower limit is unknown, it does not preclude the application of doctrine of equivalents
    • USSC thinks the burden should be placed on the patent holder to establish the reason for an amendment during prosecution
      • If none is given it should be assumed that it was related to patentability
  • Doctrine does not require proof of intent
  • Warner's final argument is that the doctrine should be limited to equivalents disclosed within the patent
    • Also should be limited to those known at the time of the patent
    • USSC rejects both of these ideas
  • USSC agrees with the Federal Circuit that juries should apply the doctrine but they do not decide it here


  • Considerations for applying doctrine
    • Patent's context
    • Prior art
    • Purpose for which an ingredient is used, etc.
    • Whether a person reasonable skilled in the art would know the interchangeability of an ingredient
  • Intent plays no role in the doctrine's application
  • Proper time for evaluating knowledge of interchangeability is at the time of infringement, not the patent
  • 1952 Patent Act is not materially different from the 1870 Act with regard to claiming, reissue, and the role of the PTO
  • Section 112 allows "means" claims
  • Prosecuting history estoppel places limits on the doctrine and insulates it from conflict with the Patent Act
  • Triple identity test
    • Function served by an element, the way it serves that function, and the result thus obtained
    • Good for mechanical but not other products and processes
  • Insubstantial differences test
    • Offers little guidance to what is insubstantial

Concurring judges

  • Have to be careful that this new presumption does not unfairly discount the expectations of a patentee who had no notice of such a presumption at the time of patent prosecution

Class Notes

Class Notes