In Ontario, claims that a lawyer made an error in handling a client’s case are tested under the law of professional negligence. These claims are often referred to as “lawyer negligence” or “ professional malpractice”. While clients may feel strongly that their lawyer’s conduct them harm, Ontario courts apply a structured and demanding legal test before holding a lawyer liable.
The recent case of Vacaru v. Legge, 2025 ONCA 856 (CanLII) https://canlii.ca/t/kgxgw illustrates the legal principles governing such allegations and the high burden that a client must meet.
A client who alleges that their lawyer made an error bears the onus of proving each element of negligence. The client must establish that (1) the lawyer breached the applicable standard of care and (2) the breach caused the client’s loss.
Failure to prove either element is fatal to the claim.
Ontario courts have consistently held that lawyers are not guarantors of results. The law recognizes that legal work often involves judgment calls, time pressures, and uncertain outcomes. To establish a breach of the standard of care, two key principles apply:
1. Reasonable Skill and Knowledge: A lawyer is required to bring reasonable skill and knowledge to the performance of the professional services he or she has undertaken to perform. This does not mean exceptional skill or flawless execution, but rather the competence expected of a reasonably capable lawyer practicing in the relevant area of law.
2. Context: The reasonableness of a lawyer’s conduct must be assessed in light of all the surrounding circumstances, including the time available to complete the work, the nature and scope of the client’s instructions and the client’s experience and sophistication. This contextual approach was articulated in Marcus v. Cochrane, 2012 ONSC 146, and recognizes that legal practice does not occur in a vacuum.
Importantly, Ontario courts have repeatedly emphasized that lawyers are not held to a standard of perfection. As the Court of Appeal stated in Folland v. Reardon, 2005 CanLII 1403 (ONCA), the standard requires a lawyer to exercise the effort, knowledge, and insight of a reasonably competent lawyer.
The court must also avoid judging the lawyer’s conduct with the benefit of hindsight. Decisions that appear mistaken after the fact may nonetheless have been reasonable when made.
Then there’s the doctrine of causation – proving that the lawyer’s error was what caused the client’s losses. Even if a client establishes that a lawyer breached the standard of care, the claim will still fail unless the client proves causation. The client must establish a clear causal link between the lawyer’s specific act or omission, and the actual financial or legal loss suffered. Ontario courts require a client who proves duty, breach, and damage to still be unsuccessful unless this causal connection is established.
Ontario law sets a rigorous standard for claims alleging lawyer error. Clients must do more than show that their case had an unfavourable outcome or that a different approach might have produced a better result. They must prove that the lawyer fell below the standard of a reasonably competent lawyer and that this failure directly caused their loss.
Legal malpractice claims are fact-specific, context-driven, and carefully scrutinized by the courts. The law strikes a balance between protecting clients from genuine professional negligence and recognizing the realities and complexities of legal practice.
This article was recently published in LexisNexis’ LAW360 at: https://www.law360.ca/ca/family/articles/2430181/when-a-client-claims-their-lawyer-s-mistakes-caused-them-losses
Steve Benmor, B.Sc., LL.B., LL.M. (Family Law), C.S., Cert.F.Med., C.Arb., FDRP PC, Acc.D.C., is the founder and principal lawyer of Benmor Family Law Group, a boutique matrimonial law firm in downtown Toronto. He is a Certified Specialist in Family Law, a Certified Specialist in Parenting Coordination and was admitted as a Fellow to the prestigious International Academy of Family Lawyers. Steve is regularly retained as a Divorce Mediator/Arbitrator and Parenting Coordinator. Steve uses his 30 years of in-depth knowledge of family law, court-room experience and expert problem-solving skills in Divorce Mediation/Arbitration to help spouses reach fair, fast and cooperative divorce settlements without the financial losses, emotional costs and lengthy delays from divorce court.
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