Sandoval was born in Washington, D.C. He began working as a professional actor in 1975 when he joined a mime school in Albuquerque, New Mexico. He later joined the troupe full time and continued his study of mime. He began his film career in the early 1980s. He had small roles in such acclaimed films Do the Right Thing, Jungle Fever, and Jurassic Park. After appearing in Clear and Present Danger in 1994, he began to take on larger roles, and appeared in Get Shorty, Up Close & Personal, and Blow.
Having appeared briefly in Repo Man and Sid and Nancy, Sandoval has also played the major roles of Treviranus (in Death and the Compass), Bennie Reyes (in Three Businessmen) and Arizona Gray (in the microfeature Repo Chick) for director Alex Cox. In addition to film, Sandoval has acted in numerous television shows, often in recurring roles. Though shows such as The Court and Kingpin failed, he found a success with Medium in 2005, where he played D.A. Manuel Devalos until the series ended in 2011. Sandoval's other guest starring roles include appearances in popular series such as Frasier, ER, The X-Files, Seinfeld and Lois & Clark: The New Adventures of Superman. He was prominently featured in the first season of the ABC drama Murder One.
Sandoval has recently moved into directing, taking the helm for the third season Medium episode Whatever Possessed You which aired in March 2007. He has since directed one episode in each of seasons four through seven.
He also co-starred as Judge Hernandez in the new comedy Bad Judge, an American legal comedy television series that was co-created by Chad Kultgen and Anne Heche. It premiered on NBC on Oct 02, 2014.