I recently had the pleasure of watching a very skilled young defence lawyer deliver a closing in defence of a solicitor sued for professional negligence in a personal-injury matter. He displayed the skill and finesse I have seen with the most senior of counsel.

The precision of that closing—and the law it marshalled—prompted this piece. The short message is blunt. In professional-negligence litigation, you almost always need expert evidence to establish the standard of care. Without it, you’re swinging blind.

The Baseline: Competence, Not Perfection

Canadian law holds professionals to the conduct of the reasonably competent peer—not to a standard of perfection. The Supreme Court’s long-standing formulation in Central & Eastern Trust Co. v. Rafuse 1986 CanLII 29 (SCC), [1986] 2 SCR 147^[1] captured it crisply. The duty is reasonable care, skill, and knowledge, grounded in what a prudent professional would do in like circumstances.

The General Rule: You Need Expert Evidence

Ontario’s Court of Appeal has made this point repeatedly.

In Krawchuk v. Scherbak 2011 ONCA 352^[2], a purchaser relied on a seller’s property-information form and a dual-agent realtor to buy a house that later revealed serious structural defects. On appeal, the agent and brokerage were held liable alongside the vendors for failing to verify the sellers’ assurances or recommend an inspection. The Court held that, as a general matter, a trial judge should not determine a professional standard of care without expert evidence. Why? Because the “standard” in a specialized field is proved, not intuited. Courts shouldn’t become their own experts, subject to two narrow exceptions (non-technical matters; or egregious conduct)^[3].

That Krawchuk proposition is routinely relied on in Ontario for professionals (including lawyers)^[4].

The Two Narrow Exceptions

First, when the issue is non-technical—the sort of thing a layperson understands—courts may dispense with experts.

Second, when the defendant’s conduct is egregious, that is so plainly below any acceptable standard that you don’t need someone in the guild to say so, expert evidence may be unnecessary.

Both exceptions come from Krawchuk and are applied sparingly.

How Courts Are Actually Applying the Rule (Recent Illustrations)

Solicitors’ negligence (Ontario)

In Yormak v. LeDroit 2022 ONSC 4615^[5], a former client who had lost a partial summary-judgment motion in litigation over unpaid tax debts sued his lawyers for negligent strategy. The court dismissed the claim, holding that the absence of standard-of-care expert evidence was fatal and reiterating that judges are not free to act as their own experts in solicitor’s-negligence cases

“Improvident settlement” claims

In Hopkins v. Murphy 2024 ONSC 3698^[6], the court dismissed a negligence claim alleging a lawyer’s settlement advice fell outside the reasonable range. The plaintiff ran into two walls, specifically no standard-of-care expert and no “trial within a trial” to show what the underlying action would likely have yielded. The decision is a pragmatic reminder that expert opinion anchors both liability and the “range of reasonable choices” analysis.

I found a recent practitioner write-up emphasizing those same points for risk management in estates and civil files very instructive as well^[7].

Small Claims still means real standards

Even at modest monetary limits, the rule bites. In Estate of Thankamma Mathi v. Juriansz 2024 ONSCSM 10495^[8], the Small Claims Court refused to second-guess a solicitor’s capacity assessment, conflict/ILA advice, or protective steps without expert evidence, none of which qualified as “non-technical,” and nothing about the conduct was “egregious” on its face.

Outside Ontario, same story

Alberta courts have cautioned that it will be a “rare case” where a judge can find lawyer negligence without expert help, a theme picking up British Columbia authorities like Zink v. Adrian 2005 BCCA 93^[9] and Alberta’s Mraz v. Herman 2016 ABCA 313^[10].

Why This Rule Exists (and Why It’s Not Going Anywhere)

Standards of professional practice evolve inside disciplines. What’s “careful” conveyancing in a conflict-tinged transfer? What’s “reasonable” case-assessment before recommending settlement? What due-diligence steps are “usual or customary” for a realtor confronted with red-flag defects? Those aren’t gut calls. They’re proved through people who actually do the work, subject to cross-examination, not through judicial instinct or counsel rhetoric.

That’s exactly why Krawchuk’s framework has stuck and spread.

Strategy: What Litigators Need to Do

For plaintiffs, retain a qualified expert early and make them central. Frame the opinion around what similar professionals do in the real world on similar facts, and tie each alleged misstep to a concrete departure. In cases attacking settlement advice, be ready to run the “trial within a trial” to show outcome and quantum. Even a persuasive expert won’t save a claim that never establishes the underlying merits. Hopkins is your cautionary tale.

For defendants, press the threshold. If the pleading squarely targets technical judgments (capacity screening, ILA/conflict management, file strategy, valuation), force the plaintiff to commit to an expert and the discipline-specific standard. If they don’t, move for judgment. Use Yormak-style reasoning to keep the judge from playing expert, and line up your own standard-bearer in case the matter proceeds.

The Two Exceptions, Applied with Restraint

Don’t over-read the carve-outs. Non-technical means truly everyday, something any juror would know without professional context. Egregious means the conduct is so obviously out-of-bounds that no one needs a map to see the cliff. Those are rare. Most allegations in professional cases are grounded in judgment calls, policies, and customary practice. This is terrain where experts are the compass, not optional add-ons.

Bottom Line

If you’re suing a professional in Ontario (or defending one), don’t treat expert evidence as a luxury. It’s the price of admission. The law has been consistent about that for decades and shows no appetite for improvisation.

Bring an expert—or don’t bother.