A member of the Philippine Bar, Atty. Leoncini graduated from Ateneo de Manila University School of Law. He is currently the 2018 class representative of the Ateneo Law Alumni Association Inc. He also holds a Bachelor of Science – Physics minor in Finance from De La Salle University – Manila on a scholarship.

Atty. Leoncini has extensive experience in working for the public sector through his stint with the Office of the Solicitor General, Metro Manila Development Authority, and the Department of Justice. He has also worked for the private sector through his internship with the Chief Justice Claudio Teehankee Center for the Rule of Law. He is currently the head legal counsel of an energy company.

Atty. Leoncini is currently handling the Firm’s civil and criminal litigation for both prosecution and defense. He is also one of the authors of Moral Governance: An Introduction to Bangsamoro Organic Law (2021).