Callejo, who served in the judiciary for 21 years, passed the Bar in 1962. He started with the Jose W. Diokno Law Office and eventually became the head of the firm’s trial department.
Callejo later on became a partner in the Montenegro, Madayag, and Hernandez Law Office until his appointment to the judiciary in 1986.
Callejo first served as regional trial court judge of Manila from 1986 until his appointment to the Court of Appeals in 1994.
He was named Outstanding Judge of Manila twice – in 1991 and 1994.
Callejo was later appointed associate justice in the Court of Appeals on Nov. 4, 1994 and to the Supreme Court on Sept. 3, 2002.
Callejo also taught criminal and remedial law at the San Beda College, Arellano University, Ateneo de Manila University, and the Far Eastern University from 1987 to 2000.
He was also a lecturer in the Remedial Law Institute of the University of the Philippines Law Center.
Callejo is currently the chairman of the Department of Criminal Law of the Philippine Judicial Academy, a position that he has held since 1998. – Sandy Araneta