Hernán is a lawyer with a long-standing career. He has worked in various banks, financial institutions, and law firms. In 1995, he joined the Chilean State Defense Council in the newly created Division for the Control of Illicit Drug Trafficking and Money Laundering, eventually becoming Chief Counsel, earning international recognition for his performance. Additionally, Hernán has focused on consulting in the design of risk prevention models, training, and certification of corporate criminal liability prevention models. He has extensive experience in civil and criminal litigation, banking and financial matters, antitrust law, and constitutional justice.

He has been a member of Chile's official delegations to the Global Forum on Fighting Corruption, the Inter-American Drug Abuse Control Commission, the World Economic Forum, and the Organized Crime Analysis Group. Hernán has also been active in the academic field, serving as Academic Director of the Law School at Universidad Mayor and teaching various courses. Moreover, he has been a speaker at several conferences and seminars in different countries.