SAN ANTONIO -- Jurors began deliberating Wednesday in the capital murder trial of a former Border Patrol agent who confessed to killing four sex workers in 2018 because he wanted to clean up the streets of his South Texas hometown.

Juan David Ortiz, 39, faces life in prison if convicted of capital murder in the slayings that took place over a two-week span. Ortiz was a Border Patrol intel supervisor at the time of his arrest. He's accused of killing Melissa Ramirez, 29, Claudine Anne Luera, 42, Guiselda Alicia Cantu, 35, and Janelle Ortiz, 28.

The judge told jurors Wednesday that they could consider a murder charge in each death.

"It is terrifying to have the enemy within the ranks of law enforcement," Webb County District Attorney Isidro Alaniz said during closing statements.

During the trial that began last week, jurors heard Juan David Ortiz's confession during a lengthy interview with investigators.

The women were sex workers who frequented the same street in Laredo. In the interview, Ortiz said he'd been a customer of most of them but he also expressed disdain for sex workers, referring to them as "trash" and "so dirty" and telling investigators he wanted to "clean up the streets."

He told investigators that "the monster would come out" as he drove along a stretch of street in Laredo that the women frequented.

In closing statements, defence attorneys said Ortiz's confession should not be considered because he was improperly induced to give it, and said at one point he didn't want to talk. Defence attorney Joel Perez argued that Ortiz, a Navy veteran, was suffering from post-traumatic stress disorder from a deployment to Iraq, had been suffering from insomnia, nightmares and headaches, and was medicated and had been drinking that night.

"He's not in his best state of mind," Perez said.

Prosecutors told jurors during closing statements it was a legal confession by an educated senior law enforcement official who was not having a mental breakdown.

"He could have stopped talking. He could have asked for a lawyer and he never did," Webb County Assistant District Attorney Karina Rios said.

Ortiz's arrest was set in motion when a woman fled from him after he pointed a gun at her in his truck at a gas station. As Erika Pena ran to a state trooper who was refueling his vehicle, Ortiz fled.

Pena, now 31, testified that after Ortiz picked her up on Sept. 14, 2018, she began to get a bad feeling. She said he told her he was the "next to last person" to have sex with Ramirez, who had been found slain the week earlier, and he was worried investigators would find his DNA.

"It made me think that he was the one who might have been murdering," Pena told the jury.

Luera was fatally shot on Sept. 13, 2018.

Authorities tracked Ortiz to a hotel parking garage in the early hours of Sept. 15, 2018, and he was arrested. During the confession, Ortiz described killing Cantu and Janelle Ortiz just hours earlier. An investigator testified it wasn't until his confession that they learned about the slaying of Janelle Ortiz.

Webb County Medical Examiner Corinne Stern testified that Ramirez, Luna and Janelle Ortiz died of gunshot wounds while Cantu, who was shot in the neck, died of blunt force trauma to the head.

The bullets collected from the crime scenes came from the same gun, and matched the weapon found in Juan David Ortiz's pickup, a ballistics expert testified.

The trial was held in San Antonio, in Bexar County, following a defence request to move the trial from Webb County due to extensive media coverage.