View source for EB:Warner-Jenkinson Company v. Hilton Davis Chemical Co., 520 US 17 (1997)

==The Situation==
*Hilton has patent on a method for ultrapurification of dyes from pH 6-9. Warner develops a similar invention at pH 5. 
*Hilton sues Warner for infringement

==The Decision==
*Trial Court found infringement, CAFC affirmed that decision
*Supreme Court sets a few new rules regarding the doctrine of equivalents, but then remands the decision back to trial court.

==In Class==
Issue #1: Is there still a doctrine of equivalents? Answer = yes! 
*Argument for getting rid of it: Section 112 places statutory burden on the patentee to establish their claims specifically; inconsistent with administrative role of PTO to set bounds on claims; it circumvents the reissue process
*Nonetheless, the Supreme Court upheld the doctrine
**However, they do express concern about the doctrine taking on a "life of its own" - meaning there has to be some limit on the expansion of claims - thus, one method of solving this dilemma was to consider each claim of an invention element-by-element rather than considering the invention as a whole. If you look at an invention overall it is easier to see "substantially the same..." but there may be distinct differences hidden within the individual elements of the invention. Thus, if you look at each element, you get a narrower application of the doctrine of equivalents, successfully checking its power.
**Seems like this narrowing doesn't really solve the 5 v. 6 aspect of the case; you would have gotten down to 5 v. 6 regardless of this narrower specification
**Also seems like the importance of an element in the claims (whether it distinguishes the patent from the prior art) should be considered when applying the doctrine. The pH of 9 distinguished the patent from prior art, but 6 was seemingly arbitrary - so should pH be a defining characteristic? This leaves much room for interpretation
*Because there was no specific reason given for the lower pH limit, it was assumed that there was some important reason - but, the patentee can get around that assumption if they can prove that they just arbitrarily made the distinction.

*The new part of the law = "element-by-element" application of doctrine & the "fuzzy" allowance of proof regarding arbitrary limitations (6pH)
**Note: Supreme Court did not actually say anything about the infringement (read as: Hilton can produce a reason for his lower limit which is sufficient to use doc. of equivalents - the reason=there is no reason - pH of 6 was arbitrary and thus the doc. of equivalents should not be stopped)
***You could potentially prove that by showing experimentally that the lower pH actually varies from 5.5-6.5...just an idea, whatever.

*I'm inclined to side with the more strict interpretation of this case - you set the boundary at pH 6, so deal with it. However, I still maintain that the doctrine is important in cases when there are ambiguous claims
 
*"en blanc" - trial is in front of the whole court of judges rather than the usual three, happens when something is really important