Mendoza became a member of the Bench in 1989 when he was appointed presiding judge of the Regional Trial Court of Santa Cruz, Laguna.

One of his well-known decisions as an appellate justice was the reinstatement of the criminal charges against millionaire businessman Dante Tan, an ally of former President Joseph Estrada who was involved in a stock price manipulation scandal.

Together with nine of the 15-member tribunal, he invalidated the executive order because of its apparent transgression of the equal protection clause for singling out the Arroyo administration.

In his ponencia, Mendoza blatantly tagged Aquino's Truth Commission "as a vehicle for vindictiveness and selective retribution."

Mendoza nonetheless upheld the validity of the remaining provisions of the RH Law despite his strong affiliation with the influential Catholic Church.