Survey Says... Decertify

April 4, 2017

In Plaunt v. Renfrew Power Generation Inc., the Ontario Superior Court of Justice decertified a class action for trespass on the grounds that new evidence obtained post-certification demonstrated that class members’ claims for trespass were dominated by individual issues, such that a class action was not actually a preferable procedure for resolving those claims.  


 The central issue in Plaunt - which case was brought on behalf of approximately 400 cottage owners in Round Lake, Ontario – was whether class members’ shoreline had been eroded because Renfrew Power Generation Inc. (RPG) and/or its predecessors raised the level of Round Lake in a way that amounted to a trespass: by storing water on their land. 

 At the original certification motion, neither party led evidence of deeds or surveys showing the boundary of class members’ lands. Following the hearing of the certification motion, the plaintiffs and defendant each retained surveyors to secure expert evidence of the legal description and boundaries of class members’ lands.

On the basis of the survey evidence, the defendant brought a motion to decertify the class action on the grounds the conditions for certifying a class action under s. 5(1) of the CPA no longer apply.

The plaintiffs objected to the defendant’s bringing a decertification motion, arguing that they were estopped from doing so because: (i) the defendants could have, but failed, to present survey evidence at the original certification motion; and (ii) the motion to decertify is amounts to an impermissible, late-filed appeal of the merits of the certification decision.


First, relying on s. 10(1) of the Class Proceedings Act, 1992 which grants the court the authority to amend the certification order or decertify the proceeding, the Court re-affirmed that it had “the authority to reopen and reconsider the question of whether the requirements for certification were still satisfied in light of new evidence, subsequent facts, or developments.”[1] The Court found that the newly obtained survey evidence in both parties’ expert report qualified under the foregoing test, warranting a re-opening and reconsideration of the certification decision in light of that evidence.

Second, the Court held that RPG was not estopped from bringing the decertification motion, because “the common issue as certified arose out of the plaintiffs’ submissions at the certification motion and it was not reasonable for the Defendant to have produced evidence directly related to this common issue before the original certification motion.”[2]

Third, the Court found that the survey evidence demonstrated that the class members’ claims  lacked the “substantial common ingredient” that was necessary in order to certify the proceeding.  This was because, as a consequence of the new survey evidence, it became apparent that the issue of trespass could not be determined on the basis of common evidence but would instead, require evidence from each individual cottage owner to determine the legal boundaries of the property they purchased, and to determine whether water covers part of their property.

In the result, the Court held “that common issue as certified for the class as presently defined does not meet the criteria of s. 5(1) of the CPA because the common issue is not a necessary or a substantial ingredient of each class members’ claim”.[3]


  • The Court has the authority to re-open and reconsider certification in light of new evidence, subsequent facts or developments, including new expert evidence. Such a reconsideration is not tantamount to a collateral appeal of the certification decision.
  • Defendants are not estopped from bringing motions to decertify a class action on the basis of newly obtained expert evidence, at least where it was not reasonable for the defendants to have produced such evidence at the original certification motion.


[1] Plaunt at para. 9. See also Pearson v. Inco Ltd., 2009 CarswellOnt 1000 (Ont. Sup. Ct.).

[2] Ibid at para. 19.

[3] Ibid at para. 21.

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