"The water is over the bridge... The Doctor knows..."
Little is known about Cesar's early life, other than he was born on February 6, 1982, and had a violent temper. He was an ex-convict, being arrested and charged for robbery in 2004, for which he was sentenced five to ten years in prison. During his incarceration, he was involved in dozens of assaults with other inmates. When he was released, he was taken under the wing of Marvin Caul, who led a group of homeless people that was committing numerous pick-pocketing crimes. Marvin came to manipulate Cesar into becoming his second-in-command, who was responsible for his future murders. All the while, Cesar started referring to Marvin as "The Doctor", likely an element of the hypnosis Marvin placed on him.
After being persuaded by Marvin to kill two women, both of whom were about to leave the organization (an act that insulted Marvin), Cesar welcomes Finn Bailey into the group after he is vouched by Marvin himself. He later kills Elijah Hall, an acquaintance of his who was also preparing to leave the organization. When he finds out that another new member of the organization, Sarah Renfield, is a reporter, Cesar knocks her out and intends to kill her, but is convinced by Marvin to let Finn, who vouched for her, handle her himself. The BAU later deduce that Cesar was responsible for the murders and arrest him in the sewer tunnels after he tries to kill JJ with a pipe. They then figure out that Marvin was his manipulator and, after Reid interrogates Cesar, pretending to have been sent by Marvin in order to gain his trust, later arrest him as well before Finn could kill him for killing his sister Carrie.
Cesar targeted people who were about to leave Marvin's organization, under orders from Marvin himself, and would subdue them with blunt-force trauma. He then killed his first two victims (who were both coincidentally brunette Caucasian women in their thirties) by chaining them to a pipe and leaving them for dead when a severe storm would flood the sewer flood control tunnels, effectively drowning them, before disposing their bodies at the construction site where Marvin buried his sole victim. He was then forced to kill Elijah Hall by strangling him due to an absence of an incoming storm, and dumped his body at a different location afterwards (presumably because Marvin found out that the bodies of Cesar's first two victims were found and the authorities were now investigating the murders). After dumping the bodies of his second two murder victims, he would then leave behind '2/10' (as a reference to the hobo code "Two eyes on ten fingers"), a warning sign for other homeless men about the punishment of thieves. How he planned to kill Sarah Renfield is unknown, but it is likely he planned on strangling her as well, since there wasn't any mention of an upcoming storm. When he attempted to kill JJ, he tried to ambush her in the sewers and bludgeon her with a pipe.
No official profile of Cesar was made by the BAU, since the profile they gave was more consistent with Marvin. However, the team deduced that he was not capable of committing the murders alone, since they required patience, planning, and organization. During his interrogation, he stated "The water' over the bridge", which is the opposite of the expression "Water under the bridge". From this, his statement would mean "Something would not be forgiven and forgotten". This mindset is consistent with the murders being motivated by revenge. Cesar drowning his first two victims might also be symbolic to the altered expression.
- January 10, 2004: An unspecified charge of robbery
- Unspecified dates from 2004 to 2014(?): Nineteen unspecified assaults in prison
- February 8: Renee Sheffield (drowned)
- February 21: Frida Bancroft (drowned like the previous victim; painted '2/10' at the dump site)
- February 22: Elijah Hall (strangled instead of being drowned; dumped his body in a different location; painted '2/10' at the dump site like the previous victim)
- February 23:
- Sarah Renfield (assaulted and intended to strangle)
- Jennifer Jareau (attempted to bludgeon with a pipe)