What is inversion test for determining ratio decidendi?

 In order to determine this aspect, one of the well-established tests is "The Inversion Test" propounded inter alia by Eugene Wambaugh, a Professor at The Harvard Law School, who published a classic text book called "The Study of Cases"25 in the year 1892. This text book propounded inter alia what is known as the "Wambaugh Test" or "The Inversion Test" as the means of judicial interpretation. "The Inversion Test" is used to identify the ratio decidendi in any judgment. The central idea, in the words of Professor Wambaugh, is as under:

In order to make the test, let him first frame carefully the supposed proposition of law. Let him then insert in the proposition a word reversing its meaning. Let him then inquire whether, if the court had conceived this new proposition to be good, and had had it in mind, the decision could have been the same. If the answer be affirmative, then, however excellent the original proposition may be, the case is not a precedent for that proposition, but if the answer be negative the case is a precedent for the original proposition and possibly for other propositions also.26

103. In order to test whether a particular proposition of law is to be treated as the ratio decidendi of the case, the proposition is to be inversed, i.e., to remove from the text of the judgment as if it did not exist. If the conclusion of the case would still have been the same even without examining the proposition, then it cannot be regarded as the ratio decidendi of the case. This test has been followed to imply that the ratio decidendi is what is absolutely necessary for the decision of the case. "In order that an opinion may have the weight of a at pg. 17 precedent", according to John Chipman Grey27, "it must be an opinion, the formation of which, is necessary for the decision of a particular case."

IN THE SUPREME COURT OF INDIA

Civil Appeal Nos. 14697, 13451 of 2015, 

Decided On: 12.04.2018

State of Gujarat Vs.Utility Users' Welfare Association and Ors.

Hon'ble Judges/Coram:

Jasti Chelameswar and Sanjay Kishan Kaul, JJ.

Citation:(2018) 6 SCC 21.

Read full judgment here: Click here

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