Mr Walsh is currently Deputy Law Officer of the International Law Division of the Department of Justice, Hong Kong and Head of the Central Authority for international cooperation in criminal matters. Mr Walsh leads negotiations on behalf of the HKSAR Government for bilateral agreements on international cooperation and advises on the application of multilateral penal conventions to Hong Kong, such as the United Nations Convention Against Corruption and the United Nations Convention Against Transnational Organised Crime, as well as a range of policy issues affecting international criminal justice.

Mr Walsh participates as a representative of Hong Kong, China in the Financial Action Task Force Against Money Laundering (FATF) and has recently completed a two-year appointment as co-Chair of a FATF Expert Group reviewing the international standards of the FATF 40 + 9 Recommendations including those relating to international cooperation.

Mr Walsh is an advisory editor and contributor to the criminal law text Archbold Hong Kong Criminal Law Pleading Evidence & Practice and appears as an advocate before the courts of Hong Kong including on behalf of foreign governments in cases involving fugitive offenders, proceeds of crime and other forms of mutual legal assistance. He is a regular speaker at international conferences and seminars on international cooperation.