A Will County judge will decide whether a Joliet man committed first-degree murder or was acting in self-defense during a 2021 incident in which a teen was shot and killed.

The trial of Cristian Ortiz-Arias, 21, of Joliet, began Wednesday with testimony from the sister of Diego Arriaga, 17; a truck driver who found Arriaga’s body; and two officers who responded to the scene.

Prosecutors alleged that Ortiz-Arias shot and killed Arriaga on May 22, 2021, in the rear parking lot of Blue Kangaroo laundromat, 606 E. Cass St.

Some time after the shooting, Arriaga’s body was found by a truck driver who was going to the laundromat with his wife for laundry.

Arriaga was shot three times in the back, and he was lying facedown on the ground, prosecutors have said.

Ortiz-Arias was 17 at the time of the incident. He is accused of pressuring two witnesses to get rid of evidence connecting him to the crime and trying to flee to Missouri, prosecutors alleged.

Ortiz-Arias’ attorney, Chuck Bretz, contends that Arriaga was the “aggressor” in the incident and his client was acting in self-defense. He said every person has a right to defend themselves, even “in the middle of a drug deal.”

“The law allows [Ortiz-Arias] to protect himself, and that’s what he did,” Bretz said.

The trial likely will hinge on the testimony of the two witnesses who were inside the vehicle with Ortiz-Arias during the shooting.

Judge Amy Christiansen, a former public defender, will decide Ortiz-Arias’ fate. Prosecutors are expected to finish their case by Monday at the latest.

Prosecutors dismissed two counts of aggravated unlawful use of a weapon against Ortiz-Arias. They are proceeding on the charge of first-degree murder and unlawful possession of a firearm.

During opening statements, Will County Assistant State’s Attorney Jacob Kreutzer said Ortiz-Arias had contacted two people to pick him up because he wanted a meal from McDonald’s, 508 E. Cass St., Joliet.

After visiting the McDonald’s, there was a “change of plans,” Kreutzer said.

Ortiz-Arias then asked the witnesses to take him to the rear parking lot of Blue Kangaroo because he had to “go pick something up.”

Ortiz-Arias wanted to go there to buy “cannabis cartridges,” Kreutzer said. While he was there, he got into an argument with someone later identified as Arriaga, Kreutzer said.

During the argument, one of the witnesses in the vehicle with Ortiz-Arias heard gunshots “blazing from the back seat,” Kreutzer said.

After the shooting, Ortiz-Arias told the witnesses to drop him off at another location, Kreutzer said. Later on, Ortiz-Arias told the witnesses to never speak of the incident to anyone, Kreutzer said.

Ortiz-Arias also told them to get rid of the shell casings inside the vehicle, the vehicle and the license plate, Kreutzer said.

But the witnesses eventually went to police about the incident, Kreutzer said.

Ortiz-Arias fired four shots, and three of them struck Arriaga, Kreutzer said.

“And what was this all over? Cannabis?” Kreutzer said.

He said Arriaga was a “17-year-old kid” who had his “whole life ahead of him.”

Bretz said the incident was a “tragedy to be sure,” but prosecutors neglected to mention that one of the witnesses saw Arriaga reaching for his waist, seemingly as if he was reaching for a firearm.

At a previous pretrial hearing in the case, Bretz suggested that Arriaga was trying to rob Ortiz-Arias and a struggle took place during their encounter, court records show.