A member of the Philippine Bar, Atty. Leoncini graduated from the Ateneo de Manila University School of Law. He holds a Bachelor of Science in Physics, with a minor in Finance, from De La Salle University – Manila, where he was a scholarship grantee.

Atty. Leoncini has extensive experience in the public sector, having served with the Office of the Solicitor General. He is currently the Head Legal Counsel of an energy company.

Atty. Leoncini handles both civil and criminal litigation for the Firm, representing clients in both prosecution and defense. He is also a co-author of Moral Governance: An Introduction to Bangsamoro Organic Law (2021).