Jiminez was born and raised in Mexico City before fleeing to the United States when he found himself on the losing side of a war between drug cartels. He spent twenty years in Los Angeles's Eastside, working in a clinic for the poor. When the Freaker outbreak occurred, Jiminez was heartened to witness the city's gangs putting aside their differences and working together in fighting the Freakers. Eventually Los Angeles fell, Jiminez fled north and found his way to Oregon, where he joined the Militia and serving as its only doctor.
When Deacon St. John joined the Militia, Jiminez conducted his examination in which he immediately saw through the drifter being more than he seems. He help treated Deacon's burnt arm that was inflicted by Carlos.
Doc Jiminez was unfortunately murdered by Private Wade Taylor, who slit his throat, when he caught Taylor stealing drugs from the infirmary. Jiminez's death made a deleterious impact on Garrett's psyche, leading him to moving all skilled personnel with R&D purpose to the Ark, including Weaver and Sarah, and eventually his so-called crusade against other survivor settlements.
Doc Jiminez was perhaps one of the most nicest people at the camp Deacon will interact with- Jiminez is seen tending to many wounded and showing great passion when doing so. He even insists Deacon comes back once in awhile so he can check his maimed arm and monitor his health.