He was a notorious drug dealer who operated alongside Lipsey and Welsh under orders from Hector Estrada, who had many connections throughout Miami. This drug organization became the prime target of Detective Harry Morgan prior to the series. Santos was also directly responsible for the murder of Laura Moser (Dexter's mother), along with the deaths of three other men, although Hector Estrada is indirectly responsible, being a murderer by proxy.
During his early years as a drug dealer he worked for a local drug lord named Hector Estrada. Jimenez followed Laura Moser on a suspicion of being a snitch and this was confirmed when she was caught meeting Detective Harry Morgan, and they slept together. Hector Estrada then ordered Jimenez and two others to take her and three other junkies to a local shipping container and kill them. Jimenez did this but was able to cut a deal with police and he was included in the Witness Protection Program while the other two were imprisoned and died off. In his old age, he was ran a tavern called The Swamp in Naples, Florida, while at the same time he continued to sell cocaine.
Following Lila's advice to confront his past, Dexter found out that Jimenez was alive and went to see him with Lila West. Dexter sat at Jimenez's bar until everyone was gone to talk to him, but Jimenez got suspicious of him, grabbed a baseball bat and threatened him. Dexter took the bat away from him then beat him to a bloody pulp. Dexter wanted to kill him, but Lila talked him out of it when he called her.
Sometime afterwards, Jimenez sold cocaine to Jose Garza, a drug trafficker and murderer on the run from the FBI, but only took money from him without delivering the drugs. Later, to punish Dexter for ignoring her, Lila gave Jimenez the address of the bowling alley Dexter would be leaving. When Dexter and Lila were leaving the bowling alley, Jimenez attacked Dexter and slashed his arm with a knife. Dexter only avoided a more serious injury due to a last second warning from Lila and the quick intervention of the other men on his bowling team. However, Jimenez was still able to escape.
Following the attack, Dexter decided to abandon what Lila had taught him and kill Jimenez. The next night, Dexter waited for him outside his bar and followed him to an isolated cabin in the Everglades. Dexter turned on the radio in Jimenez's car. When Jimenez came out, Dexter injected him with tranquilizer, brought him inside the cabin and strapped him to the table. When Jimenez woke up, Dexter took the usual blood sample from him while Jimenez tried to bargain with him, offering him cocaine in exchange for his freedom. When it became obvious Dexter was not interested in bargaining, Jimenez became hostile and threatened to kill him. Dexter then duct taped his mouth shut and killed him with a chainsaw in the same way Jimenez had killed his mother.
Afterwards, Dexter had to briefly leave his body parts at the cabin because he had to go to Rita Bennett, who called to tell Dexter someone had broken in her home. He returned to dispose of them the next night, and was confronted by James Doakes. Dexter later made use of Jimenez's cabin as a makeshift prison for Doakes.
- Two different actors portrayed younger Jimenez: an uncredited actor in the first season and Roman Mitichyan in the second one. Interesting enough, the first one, who can be only briefly spot in "Seeing Red" is more similar because both he and primary Jimenez actor Tony Amendola have very prominent pockmarks on their faces, while Mitichyan doesn't (though he still has a similar face).
- Jimenez is one of the three characters Dexter both fantasized/dreamt of killing and killed in real life, others being Brian Moser and Juan Ryness. Jimenez is, however a unique case because he appeared in his dreams twice (as his younger self, neck being snapped by Dexter, and as a dismembered corpse in the other one (and dismembered differently then in real life - his head still attached) being killed both times, and also because he was the only one out of three to be killed after Dexter dreamed about it.