He was a Spanish biologist native to an isolated region of Spain and former employee of the Umbrella Corporation. 
After leaving his job and returning home, he was recruited by Osmund Saddler into the cult of Los Iluminados' research into the Plaga parasite. Unbeknownst to Dr. Serra, the true purpose of his research was to assist in the genetic strengthening of the Plaga against any possible resistance, as well as the engineering of several bio-organic weapons.