Judge Vaz began her career as an Examining Judge of the Tribunal Première Instance de Dakar. After that she was President of the Labour Tribunal in Saint Louis, Senegal; Chief of the Examining Judges in Dakar; Vice President of the Tribunal de Premiere Instance de Dakar; and a Judge at the Court of Appeal and at the Supreme Court.
In 1992, she became first President of the Court of Appeal and a year later she was appointed first President of the National Electoral Commission of Senegal. She later became President of the High Court of Senegal. In 1997 she became first President of Supreme Court. Judge Vaz has participated in several conferences, including the International Union of Magistrates, International Federation of Women Lawyers “World Peace Through the Law”; the International Commission of Jurists, and the Conference of Chief Judges of the Commonwealth and Judges of Appeal Courts. Judge Vaz was a Tutor at l’Ecole Nationale d’Administration et de Magistrature du Senegal until 1991. She was an Associate Member of the International Commission of Jurists and Member of the Permanent Court of Arbitration in The Hague, in The Netherlands. Judge Vaz is a graduate of the National Centre for Judicial Studies (Centre National d‘Etudes Judiciaires) in France (1969).
In May 2001 Judge Vaz was elected by the United Nations General Assembly as a judge to the International Criminal Tribunal for Rwanda (ICTR) in Arusha, Tanzania. She was re-elected in February 2003. She served as Presiding Judge of Trial Chamber III and Vice President (2003 to 2005) for the International Criminal Tribunal for Rwanda. Since August 2005 she has been a member of the Appeals Chamber.