Trial Begins for Border Patrol Agent Accused of Killing Four Women

In the trial that began this week, prosecutors said the victims in the case were all prostitutes working along San Bernardo Avenue, a notorious red-light district, who were picked up and taken to secluded areas, where they were shot in the back of the head.

The Webb County district attorney, Isidro Alaniz, told the jury that the victims — Melissa Ramirez, Claudine Anne Luera, Guiselda Alicia Cantu and Janelle Ortiz — were mothers, daughters and sisters with families who loved them.

He said the prosecution would present a trove of forensic evidence as well as a nine-hour videotaped confession to prove that Mr. Ortiz committed the crimes.

“The case is about a man who betrayed his badge,” Mr. Alaniz told the jury. “He betrayed his country. He betrayed his family. He betrayed his community, for his own selfish needs.”

But Joel Perez, addressing the jury for the defense, said Mr. Ortiz was not a killer but a dedicated law enforcement officer who had been erroneously identified by a woman who was under duress. At the time of his arrest, he said, Mr. Ortiz was suffering from a series of mental health problems, including depression and anxiety, and, during his purported confession, he had merely regurgitated what he had read in newspapers, in an effort to end an interrogation that had lasted for more than nine hours.

“This is a defeated man,” he said.

Mr. Ortiz, 39, wearing a black suit, gray shirt and burgundy tie, looked visibly rattled, and at times he took off his eyeglasses and shook his head as prosecutors and witnesses painted him as a predator who had targeted vulnerable victims at the margins of society.