Aguilar is an admitted member of the Acosta Plaza subset of the Norteños criminal street gang.

Alexis Aguilar's second trial for first-degree murder. Aguilar is accused of gunning down 25-year-old Jose Mexicano in March 2007 in front of Mexicano's then-10-year-old son. Aguilar was 17 at the time of the killing. The shooting has been characterized by Salinas police as gang related. According to testimony, Aguilar is an admitted member of the Acosta Plaza subset of the Norteños criminal street gang.
Mexicano, who had recently been released from prison, was affiliated with the rival Sureños gang. The first trial ended in a mistrial when the jury could not reach a unanimous verdict, voting 11-1 for conviction. Aguilar was convicted of one count of street terrorism. According to the police investigation, Mexicano and his son were walking through the Acosta Plaza neighborhood of East Salinas—which has been identified as Norteño territory—when he was confronted by Aguilar. Aguilar ordered Mexicano to remove the blue baseball cap he was wearing and to tell his son to run.
Mexicano and his son ran in different directions, and police say Aguilar opened fire, striking Mexicano once in the arm and once in the back. The second wound proved fatal. In his closing argument, prosecutor David Rabow emphasized testimony in the first trial by the victim's son, who identified Aguilar as the person who
confronted and attacked his father. Rabow also pointed to the eyewitness testimony of a Sureño gang member who placed Aguilar at the scene. He recounted statements by two fellow Norteños, identified in court as Israel and Rey, who testified that Aguilar took credit for the shooting. Rey said Aguilar gave him the murder weapon on the night of the incident, and pleaded with him later to stay quiet about the crime, saying, "If you don't testify, I'll walk." Rabow reminded the jury of evidence found on Aguilar's home computer that included a newspaper account of the murder and a photo of somebody wearing a T-shirt memorializing Mexicano. The prosecutor characterized both as "trophies" of the killing. Aguilar's motives, Rabow said, could have included revenge for an alleged burglary by Sureños, perceived disrespect by Mexicano for wearing a blue cap—Sureño color—in Norteño territory, or a desire to raise his own status within the Norteño gang by committing a high-level crime.
Defense attorney Allen Kleinkopf countered by saying the prosecution's argument for conviction was based entirely on two false premises: that the Acosta Plaza subset of the Norteños gang is a tight-knit organization with a well-defined hierarchy, and that Aguilar was the shooter. Kleinkopf assailed prosecution witnesses Rey and Israel as notorious criminals and liars who gave false statements about Aguilar in court in exchange for the prosecution's offer to reduce their own prison sentences in unrelated cases. He discounted the eyewitness testimony of Mexicano's son because the shooter reportedly had raised the hood of the sweatshirt he was wearing, so only his eyes, nose and mouth were visible to the boy, who was standing about eight feet away. He noted that the boy initially failed to identify Aguilar in court during the first trial. Kleinkopf said Aguilar had no previous arrests on weapons charges, and that bullets recovered did not necessarily match the alleged murder weapon.
He also assailed the prosecution's evidence of multiple cell phone calls made in the minutes after the murder between Aguilar, Israel, Rey and a Norteño named Juan, whom Rabow called "The Big Homey" and identified as the leader of the Acosta Plaza group. Kleinkopf argued that if somebody is shot in the Acosta Plaza neighborhood, everyone is spreading the word rapidly via cell phone. Kleinkopf attacked the computer evidence by noting that Aguilar's brother, who is not a gang member, also had access to the computer and conceivably could have downloaded the article and photo. The jurors have a choice of convicting Aguilar of first- or second-degree murder, or acquitting him. Because one juror had a scheduling conflict Friday afternoon, the jury only had about 30 minutes to deliberate.