Free World Trust v Électro Santé Inc, [2000] 2 S.C.R. 1024, 2000 SCC 66, is a leading Supreme Court of Canada decision on patents, namely claim construction and the necessity to identify essential elements and non-essential elements. Along with the related decision, Camco v. Whirlpool (2001), 9 C.P.R. (4th) 129 (SCC), the Supreme Court of Canada rejected the doctrine of equivalents applied in the United States and adopted the doctrine of purposive construction, as originally applied by the United Kingdom House of Lords in Catnic v. Hill & Smith. This was a landmark decision as it resolved the uncertainty in Canadian case law between the two doctrines. The Court also articulated the scope of protection provided by patents and the requirements for infringement. Background Electro-magnetic therapeutic system is the English title of Canadian Patent 1,113,156 which was issued in 1981. The inventors Dr. Roland A. Drolet and Gaetan Charland, both from Canada, claimed that the device was an "electro-magnetic device for treating various types of rheumatic and arthritic diseases." The invention related to a technique of bombarding human bodies with low-frequency electromagnetic waves and controlled the wave frequency using "circuit means". On November 24, 1981, Dr. Drolet and Mr. Charland received patent approval for their electro-magnetic therapeutic system. Their drawings, as portrayed within the Canadian patent, labeled the device "Ri - 2000 MAGNETOTHERAPY SYSTEM". By 1983, Dr. Drolet and Mr. Charland were issued another patent titled "ELECTRO-MAGNETIC THERAPEUTIC SYSTEM AND METHOD" which described the "Ri - 2000" in much further details and labeled the device as "Ri -2000 RHUMART-THERAPY SYSTEM". This second patent maintained many similar characteristics to the 1981 patent. In fact both patents drew and labeled their devices with "RODROL INSTRUMENTATION INC.". Free World Trust was the rightful owner of the patents of invention numbered 1,113,156 (the "'156 patent") and 1,150,361 (the "'361 patent") issued in 1981 and 1983 respectively. On December 15, 2000, in the case of Free World Trust v. Électro Santé Inc., a decision was rendered by the Supreme Court of Canada on the infringement of patents 156 and 361. The decision would create a legal precedent cited in at least 148 Canadian trials. The case was even noted in Canada for setting out "the test for patent infringement" and "the principles of purposive claim construction". The court transcripts explain that Électro Santé Inc., a competitor, developed similar technology that used a microcontroller rather than