Diego Ramirez (alias Luis Cordova) is a science teacher at the Catholic school attended by Ella Mendez, Arturo Rivera, and Tripp Raines. When Ella was raped and impregnated, Ramirez was questioned under the alias of Cordova.
It was revealed Ramirez was a registered sex offender merely from a statutory relationship with an age difference of three years when he was nineteen. He was cleared of suspicion in Ella's rape when Tripp was revealed to have raped her, and then Arturo later killed him in a rage.
Ramirez was later fired from the school when his record came forward. (SVU: "Blood Brothers")