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Contact by email at [email protected]

t. +1 416-601-8285


Law School

Osgoode Hall Law School

Bar Admission

Ontario, 2017

Leah Ostler is an associate in our Litigation Group in Toronto. Her practice focuses on defence litigation, including commercial matters, professional negligence and telecommunications. Leah represents individuals, corporations and financial institutions in complex, high-stakes disputes. She has served as junior counsel in trials and class actions up to the Court of Appeal, and as lead counsel before administrative tribunals in a wide range of complex matters.

Leah’s litigation experience includes:

  • Representing telecommunications companies and cannabis companies in proceedings on the Commercial List
  • Representing a university in a complex construction negligence matter
  • Defending a financial institution in a class action regarding trailing commissions
  • Representing professional accounting firms in civil and regulatory proceedings
  • Defending physicians in liability cases tried before judges and juries and regulatory matters before the CPSO and HPARB
  • Representing physicians in disputes with patient’s family members over psychiatric care and end-of-life treatment
  • Carroccia v. Ayow, October 2020: Second chair in the successful defence of a physician in a medical negligence jury trial – one of the first civil jury trials conducted in Ontario under COVID-19 protocols
  • McKitty v Hayani, 2019 ONCA 805: Successfully represented the respondent in the leading Canadian case on the definition of death, which confirmed that the medical and legal definition of death includes death by neurological criteria 

Leah is also member of the McCarthy Cannabis Group. The Cannabis Group partners with clients driving the transformation of the recreational private retail sector, leveraging our knowledge of the industry and regulatory environment with extensive experience advising innovators in emerging markets. Our clients include major financial institutions, leading cannabis companies, commercial property holders, food and beverage producers, and more. Leah has advised on cannabis use across the provinces, cannabis/hemp-derived CBD products under the Natural Health Products regime and US-Canada jurisdictional issues.

Leah received her J.D. from Osgoode Hall Law School, where she held executive positions with the Osgoode Women’s Network (OWN), was a Dean’s Fellow for Torts Law, and led several mentorship programs. Leah did a semester abroad at Amsterdam University, where she took Masters of Laws courses in International Law. Leah obtained her B.A. (Honours) in History and Global Development from Western University and was a Political Intern for the Department of Foreign Affairs and International Trade (DFAIT) in Ramallah, West Bank. 


  •  “Behind Masks: First Ontario civil jury trial during COVID”, The Lawyer’s Daily, December 2020

  • “The Mauritius Convention on Transparency: The Potential Impact on Canadian Investors, Commercial Litigation and Arbitration Review”, Vol. 6 (23), August 2017

Leah has co-authored several blogs and Legal Updates available on the McCarthy website.