Longo v. MacLaren Art Centre, 2014 ONCA 526:
 The relevant provisions of the Limitations Act, 2002 are as follows:
5. (1) A claim is discovered on the earlier of,
(a) the day on which the person with the claim first knew,
(i) that the injury, loss or damage had occurred,
(ii) that the injury, loss or damage was caused by or contributed to by an act or omission,
(iii) that the act or omission was that of the person against whom the claim is made, and
(iv) that, having regard to the nature of the injury, loss or damage, a proceeding would be an appropriate means to seek to remedy it; and
(b) the day on which a reasonable person with the abilities and in the circumstances of the person with the claim first ought to have known of the matters referred to in clause (a).
 The items listed in s. 5(1)(a) are conjunctive. The limitation period does not begin to run until the putative plaintiff is actually aware of all of those matters or until a reasonable person, with the abilities and in the circumstances of the plaintiff, first ought to have known of all of those matters.
 A plaintiff is required to act with due diligence in determining if he has a claim. A limitation period will not be tolled while a plaintiff sits idle and takes no steps to investigate the matters referred to in s. 5(1)(a). While some action must be taken, the nature and extent of the required action will depend on all of the circumstances of the case, as this court noted in Soper v. Southcott (1998), 111 O.A.C. 339, at p. 345 (C.A.):
Limitation periods are not enacted to be ignored. The plaintiff is required to act with due diligence in acquiring facts in order to be fully apprised of the material facts upon which a negligence or malpractice claim can be based. This includes acting with diligence in requesting and receiving a medical opinion, if required, so as not to delay the commencement of the limitation period. In some cases, a medical opinion will be necessary to know whether to institute an action. In other cases, it will be possible to know material facts without a medical opinion, and the medical opinion itself will simply be required as evidence in the litigation. In the latter instances, the time of receipt of the medical opinion is immaterial to the commencement of the running of the limitation period.
 The Soper case, which was cited by the motion judge, was decided under the previous legislation but is entirely consistent with the current legislation. The plaintiff must act reasonably in investigating and determining whether he or she has a claim. A consideration of whether the plaintiff has acted reasonably will include an analysis of not only the nature of the potential claim, but also the particular circumstances of the plaintiff.
 Certainty of a potential defendant's responsibility for an act or omission that caused or contributed to the loss is not a requirement. All that is required is that the plaintiff has prima facie grounds to infer that the acts or omissions were caused by the identified parties. The establishment of prima facie grounds may or may not necessitate obtaining an expert report: Kowal v. Shyiak, 2012 ONCA 512.