In 2004 she was appointed and sworn in as judge of Criminal Appeals of the Supreme Court for a 12-year tenure, a position she holds today. Nieves was Control Judge of Court No. 11 and judge in Courts No. 4 and No. 7 of the Court of Appeals, positions she held in the Criminal Judicial Circuit of the Metropolitan Area of Caracas.
She was also professor of Criminal Procedural Law at the Santa Maria University, where she graduated as a lawyer and as a specialist in Criminal Sciences.
In 2005, she was appointed director of the Public Defender for three consecutive terms, where she led the Congress of MERCOSUR Public Defenders.