Estate litigation has its share of legal landmines. Chief among them is the no-contest clause, a ticking grenade buried in the back of a will that many lawyers treat as decorative, until it explodes. These clauses are drafted with the best of intentions, to preserve the testator’s wishes and deter unnecessary conflict. But when mishandled, or worse, ignored, they can detonate years later, eliminating a beneficiary’s entitlement and setting off a second wave of litigation.

But what happens when a beneficiary, acting on a lawyer’s advice, unwittingly pulls the pin? The case I want to explore, rooted in real-world experience, is one where the beneficiary is advised to challenge the will or take some procedural step that, unbeknownst to them, violates the no-contest clause. Their lawyer either fails to flag the risk or downplays it. Eventually, the lawyer quietly withdraws. A second lawyer comes on board, keeps the file moving, and only when the estate trustee enforces the clause is the true impact of that initial advice revealed. At that point, two years or more have often passed. So the obvious question is this: has the limitation period expired against the first lawyer? And does the second lawyer bear any responsibility for missing the warning signs?

The law of discoverability offers some answers. Under Ontario’s Limitations Act^[1], the general rule is that a claim must be brought within two years of when the plaintiff knew, or ought to have known, that the injury, loss, or damage occurred and was caused by the act or omission of the person being sued. This “discoverability” doctrine has become a recurring theme in professional negligence cases, especially those involving lawyers.

The recent Supreme Court of Canada’s 2021 decision in Grant Thornton LLP v. New Brunswick^[2] is now the leading word on the subject. The Court made it clear that a claim is discovered, not when the plaintiff is certain of success, nor when all the facts are fully known, but when there is enough information to draw a plausible inference of liability. That is, when a reasonable person would realize that something has gone wrong and suspect that someone may be to blame.

In Grant Thornton, the province of New Brunswick issued $50 million in loan guarantees to a struggling company based on an external audit from Grant Thornton LLP, which stated that the company’s financials were materially accurate. When the company collapsed months later and the guarantees were called upon, the province retained another accounting firm to investigate. That firm found significant overstatements of the company’s assets and earnings, errors that the original auditors failed to catch. The province launched a negligence claim, but the auditors sought summary judgment, arguing the limitation period had expired.

The Court ultimately agreed with the auditors, concluding that the province had sufficient knowledge to draw a plausible inference of negligence by the time they received the second firm’s report. This was a critical clarification. Plaintiffs don’t need to know every detail or have legal certainty, but once there is enough to connect the dots reasonably, once a plaintiff knows there has been a loss, that it may have been caused by someone’s error, and who that someone is, the two-year limitation clock begins to run.

The SCC decision emphasized two key points. First, discoverability is based on material facts, not legal conclusions. A plaintiff doesn’t need to know the standard of care has been breached, just that there has been an act or omission that plausibly contributed to their harm. Second, the Court rejected any notion that plaintiffs can wait for perfect certainty or legal advice before acting. That sort of perfectionism, the Court warned, would undermine the whole purpose of limitation periods.

In the context of estate litigation, this raises difficult questions. In cases involving no-contest clauses, the triggering event may be obscure, indirect, or initially without consequence. For example, a beneficiary might file a Notice of Objection, ask for interpretive relief, or even request a formal accounting, any of which could, under some clauses, be construed as a challenge to the will. If their lawyer failed to warn them about the potential implications, and the trustee does nothing for two years, when is the claim against the lawyer discovered?

If we follow the logic of Grant Thornton, the clock starts not when the estate trustee enforces the clause, but when the beneficiary had, or should have had, enough information to suspect they had taken a triggering step and that their lawyer failed to protect them. If the clause was plainly written, if the action was recorded, and if the file shows no clear analysis of the risk, then a court may well find that a reasonably diligent client should have known earlier.

Of course, this depends on what the client knew or should have known, and that’s where the facts matter. Was the clause buried or ambiguous? Did the client rely entirely on the lawyer’s interpretation? Did the lawyer’s withdrawal leave things in a fog? Did the successor lawyer even review the will or flag the issue? Did anyone, at any point, connect the action to the risk?

The responsibilities of the second lawyer are especially under-scrutinized. In my view, they bear a duty to independently evaluate the client’s exposure, especially in a litigation file involving estate assets. If a new lawyer takes over and allows the challenge to continue without reviewing the will in full, or without advising on the possible impact of a clause, they may become part of the problem. At minimum, their involvement may restart or complicate the discoverability analysis.

Clients are often caught in the crossfire. By the time they learn that a clause has been enforced and their inheritance revoked, they may have cycled through multiple lawyers. Each one may blame the last. But for the client, the effect is the same: they’re out of the will.

In this situation, mediation can be more than just a procedural step—it can be a practical solution. Litigation between clients and former counsel is slow, expensive, and emotionally draining. When the estate is already diminished, and the conduct of multiple parties is in issue, mediation offers a chance to reconstruct the timeline, allocate responsibility, and find resolution that reflects the messy reality of the file.

The takeaway is clear: no-contest clauses are legal grenades. They should be treated with the same caution as limitation periods themselves. Clients need advice tailored to the real-world consequences of every legal step they take. And lawyers, first, second, or third in line, need to remember that their duty is not just to keep the file moving, but to make sure it’s moving in the right direction.

We can’t afford to be casual about clauses that can erase a client’s entire inheritance. The legal system may be slow, but the limitation clock isn’t. And by the time the client hears the bang, the damage may already be done.