Former Ombudsman Desierto was born on April 25, 1935 in Sitio Pasil in Cebu City. He received his secondary education at the University of San Carlos (USC) in Cebu City wherein he also took his Associate in Arts. He later obtained his Bachelor of Arts and Bachelor of Law (1957) at the University of the Philippines, Diliman. He was later admitted to the Philippine Bar in 1958.
From 1961-1974, he was engaged in the private practice of law in Cebu and Manila. He started his career in the government service when was appointed as Judge Advocate, Office of the AFP Judge Advocate General in 1974. In 1988, he was appointed Deputy Judge Advocate General.
He served as the Special Prosecutor of the Office of the Ombudsman from April 1, 1991 to August 3, 1995. On August 4, 1995, he was appointed Ombudsman by then President Fidel V. Ramos.