In Lima v. Moya and Mata v. Moya, Master Haberman provides a detailed discussion of a plaintiff’s obligations under the Limitations Act, 2002 to investigate potential parties prior to the expiry of the limitation period. The relevant paragraphs are below.
Two issues bear noting. Firstly, Master Haberman refers to the discoverability doctrine and its application to the section 4 general limitation period. Technically speaking, this is incorrect. Section 5, which is the codification of the common law principle of discoverability, determines the commencement of the general limitation period.
Secondly, Master Haberman held that a plaintiff’s obligation to take reasonable steps to investigate a potential claim can include bringing a Wagg Rule 30.10 motion (see this helpful explanation of Wagg motions). She found it “inconceivable” that personal injury counsel would be unfamiliar with this procedure for gaining access to police records, and that the failure to bring such a motion in this case “amounts to a lack of due diligence, such that discoverability cannot be relied on” (at paras. 95, 117).
 The applicable limitation period here is two years, as per s. 4, of the Act, so it expired in July 2011, subject to the application of the discoverability doctrine. The Act states that a party is presumed to have known of all necessary matters to start its claim on the day on which the act or omission on which the claim is based occurred, so that the plaintiff bears the onus of establishing that the presumption should be ousted.
A claim is discovered on the earlier of 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).
 Case law has interpreted first ought to have known to mean would have found out had they used reasonable diligence. Thus, a plaintiff is bound to start his claim within two years of becoming aware of the material facts on which it is based having been discovered, or ought to have been discovered by the plaintiff by the exercise of reasonable diligence. (see Central Trust Co. v. Rafuse 1986 CanLII 29 (SCC),  2 SCR 147).
 Where the plaintiff relies on their failure or inability to learn all of the facts they deem necessary to start their claim against a particular defendant, the onus is on him to lead cogent evidence to the effect that it would have been inappropriate or abnormal for him to have investigated further during the life of the limitation period (see Mercurio v. Smith  OJ No. 5040).
 In Aguonie v. Galion Solid Waste 1998 CanLII 954 (ON CA), 1998 CANLII 954, the Ontario Court of Appeal discussed the why discoverability was a necessary addition to the law of limitations. One of the scenarios considered was a case where the seriousness of the injuries sustained by a plaintiff was not clear within the two-year limitation period. Thus, though it might appear that a plaintiff was aware of all of the elements to allow the him to know he had a claim and against whom it should be brought within the limitation period, the essential ingredient of whether his injuries were serious enough to pass threshold may not have crystalized during that time frame. In such cases, the court was of the view that the deadline for starting the action should be extended until he could know, and discoverability principles were used as a basis for doing so.
 The Court of Appeal has also looked at cases where identifying tortfeasors was the issue, pointing out that:
The discovery of a tortfeasor involves more than the identity of one who may be liable. It involves the discovery of his or her acts, or omissions, which constitute liability.
 Again, the plaintiff will be held to a standard of having used reasonable diligence to obtain this information.
 It is also understood that, in certain types of actions, identifying possible defendants is not always a straightforward exercise. For example, in medical malpractice cases, hospital charts may be illegible or not all medical staff in an operating room or on duty in the emergency room may be identified. In slip and fall actions, it may take time to determine all possible occupiers, or those contractually bound to maintain the upkeep of the property where the accident occurred.
 It is understood that there will be cases where the plaintiff is not even aware that he is missing critical information leading to the identity of a possible defendant until examinations for discovery so he cannot be found at fault for failing to pursue further information (see Madrid v. Ivanhoe Cambridge Inc. 2010 ONSC 2235 (CanLII).
 As the court pointed out in Western Mercantile Financial Corp. v. Ernst & Young Inc., 1999 ABQB 144 (CanLII), 11, CBR (4th) 149, not every item of evidence to support the plaintiff’s claim need be known before the limitation period commences to run.
 Similarly, in Lawless v. Anderson, 2011 ONCA 102 (CanLII), the court stated:
Determining whether a person has discovered a claim is a fact-based analysis. The question to be posed is whether the prospective plaintiff knows enough facts on which to base an allegation of negligence against the defendant. If the plaintiff does, then the claim has been “discovered” and the limitation begins to run.
…Certainty of a defendant’s responsibility for the act or omission that caused or contributed to the loss is not a requirement.
 Further, in The Investment Administration Solution Inc. v. Silver Gold Glatt & Grosman LLP 2011 ONCA 658 (CanLII), the Court of Appeal pointed out that discovery of new facts that might help the plaintiff’s case does not restart the limitation period.
 In summary, as long as the identity of a potential tortfeasor is known and there is some information on which a court could make a finding of liability, there is no room for discoverability to delay the starting point of the limitation period. Having enough information to form an allegation of negligence is quite different from having a winning case against a particular defendant – it is only the former that is required for the limitation clock to start running.
 Further, while new information may emerge down the road that strengthens the case against the proposed defendant, this will not restart the clock. A plaintiff should not wait until he has a good case against a defendant before starting a claim against him – as long as he has a case he can try to make, he must move within the limitation period.
 In terms of what does and does not constitute due diligence in assessing whether grounds to sue a particular individual exist, Master Dash noted in Wakelin v. Gourley et al 2005 CanLII 23123 (ON SC), 76 OR (3d) 272, that if all the plaintiff does during the two years after an accident in order to identify tortfeasors is request a copy of the police report, that will not constitute reasonable diligence.
 The plaintiffs rely on the case law that dictates the approach the court should take when dealing with motions such as there, where the issue of discoverability is on the table and there is a credibility issue. They maintain that the case law suggests that leave should be granted to add the proposed party, while also allowing the defendant to plead the expiry of the applicable limitation period.
 However, it appears clear that such an approach is only advocated when there is an issue of credibility that has to be resolved regarding who knew what and when, such that a trial is a better mechanism for resolving the issue (see Wong v. Sherman  OJ No. 1534). The “let it go and flesh out the facts at trial” approach is only appropriate when the basis for the discoverability of the claim must be explored in more depth and the evidence about it needs to be tested.
 I should not have to point this out in 2015, the plaintiff’s only salvation in the face of an expired limitation period is the application of the discoverability doctrine. The doctrine of “special circumstances” was clearly laid to rest in Joseph v. Paramount Canada’s Wonderland, 2008 ONCA 469 (CanLII), a decision of the Ontario Court of Appeal released in February 2008. Cases that talk about lack of prejudice are generally dealing with special circumstances so the presence or absence of prejudice really is not a factor here. When dealing with discoverability, the issue is whether someone discovered, or ought to have, that they have a claim, along with the essential elements that go with it to enable them to start an action. This is a fact-based analysis [emphasis in original].