Editing Doctrine of equivalents (section)

=== United States ===
The United States also has both statutory equivalents doctrine that is codified in 35 U.S.C. § 112 ¶ 6, which extends to equivalents available at patent's issuance, and a more general (non-statutory, created by courts) doctrine of equivalents, which extends to technological equivalents developed after the patent is granted. Notably, the doctrine of equivalence can be applied even to [[means-plus-function claims]].<ref>WIPO International Patent Case Management Judicial Guide: United States. 2022. SSRN Electronic Journal. P.S. Menell, A.A. Schmitt. doi: 10.2139/ssrn.4106648. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4106648</ref> The proposed equivalents also cannot cover, or ensnare, the prior art.<ref>[http://webarchive.loc.gov/all/20140611070955/http://www.cafc.uscourts.gov/images/stories/opinions-orders/08-1240.pdf] ''Depuy Spine, Inc. v. Biedermann Motech GMBH'' (Fed. Cir. 2009)</ref>

In American practice, the doctrine of equivalents analysis is applied to individual claim limitations, not to the invention as a whole.<ref name="Warner-Jenkinson Co.">''See [[Warner-Jenkinson Co. v. Hilton Davis Chem. Co.|Warner-Jenkinson Co.]]''</ref> The legal test, articulated in ''[[Warner-Jenkinson Co. v. Hilton Davis Chem. Co.]]'' (1997), is whether the difference between the feature in the accused device and the limitation literally recited in the patent claim is "insubstantial."

One way of determining whether a difference is "insubstantial" or not is called the "triple identity" test. Under the triple-identity test, the difference between the feature in the accused device and the limitation literally recited in the patent claim may be found to be "insubstantial" if the feature in the accused device:
#Performs substantially the same function
#In substantially the same way
#To obtain the same result
as the limitation literally recited in the patent claim. See ''[[Graver Tank & Manufacturing Co. v. Linde Air Products Co.]]'', (1950).

The Court also explained that the doctrine of equivalents applies if two elements are interchangeable and a person with ordinary skill in the art would have known that the elements were interchangeable at the time of infringement.<ref name="Warner-Jenkinson Co."/>

In the United States, the doctrine of equivalents is limited by [[prosecution history estoppel]]. Under prosecution history estoppel, if the patentee abandoned through an amendment to the patent application certain literal claim coverage (e.g., by narrowing the literal scope of the patent claim), then the patentee is estopped from later arguing that the surrendered coverage is insubstantially different from the literally claimed limitation.<ref>''See [[Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.]]''</ref> Also, based on the public dedication principle, a patentee may not invoke the doctrine of equivalents to recapture subject matter disclosed but not claimed in a patent.<ref>Johnson & Johnston Assocs. Inc. v. R.E. Serv. Co., 285 F.3d 1046, 1054 (Fed. Cir. 2002)</ref>