On a cool spring night five years ago, 16-year-old Martha Puebla sat on the curb outside her Sun Valley home, talking to a friend, when a man walked up from behind.
"Who are you?" the man demanded of Puebla.
"I'm Martha," she responded. "You know me."
With that, the man pulled a 9-millimeter handgun from his sweat shirt pocket and started shooting. The fatal shot -- fired from so close that it left soot and burn marks on Puebla's cheek -- struck just below her left eye.
Alarmed by the gunfire, Puebla's mother rushed outside. "¡Dios mio! ¡Esta muerta!" the neighbors heard her cry from down the block. "My God! She's dead!"
Police swarmed the area, roping it off with yellow tape. Plastic letters marking pieces of evidence dotted the street. Cameras flashed. And, of course, there was the body. Puebla lay sprawled on her back in the street, legs splayed, eyes still open, her white sweater drenched in blood.
Martin Pinner, a homicide detective with the Los Angeles Police Department, was home that night. But when a police supervisor learned the young girl's name, he called Pinner.
Pinner and his partner, Juan Rodriguez, had been to that same dreary corner of Lull Street and Case Avenue months before to investigate the murder of another teen. They had met Puebla then.
The detectives, who were assigned the case, worked through the night and into the next morning tracking down leads. It would be years before the pieces of the case would fully come together, but in those early hours there should have been an obvious question: In trying to solve one murder, had the detectives set into motion another?
The events leading to Martha Puebla's slaying began five months earlier outside her bedroom window.
Shortly before 2 a.m. on Nov. 27, 2002, a girlfriend of Puebla's pulled up outside her house. The teenage girl, whom The Times is not identifying for her safety at the request of a prosecutor, had come with another friend, Christian Vargas. He stayed in the car while the girl went to Puebla's ground-floor window and asked if she wanted to come hang out.
As the girls talked, gunshots suddenly filled the night air. The girl jumped through the window, cowering in Puebla's room. After a few minutes, she approached the car, where she found Vargas' body riddled with bullets. He begged the girl for help and then died, his head slumped against the steering wheel.
After early interviews, suspicion fell quickly on Jose Ledesma, a member of the Vineland Boyz -- a notorious, violent gang that controlled much of the drug sales on the streets of Sun Valley. That night detectives searched his family's home. Under his mattress, they found a loaded assault rifle and letters from other Vineland Boyz, many of them written from prison.
"Peps," as Ledesma was called in the gang, wasn't there. The detectives were told that he was hanging out with another Vineland Boyz member, Mario Catalan.
The next morning, after hearing that the police had been at his house, Ledesma crossed the border with Catalan and checked into a motel in Tijuana.
Two days later, Pinner and Rodriguez caught a break.
Mexican police, responding to a domestic abuse call from a passerby, found Ledesma, Catalan and Catalan's girlfriend drunk after a day at a seaside resort town. Catalan and his girlfriend had gotten into a fight. Questioned by Mexican authorities, the woman told them that Ledesma and Catalan were wanted in Los Angeles for murder.
By nightfall, the suspects had been hauled back to LAPD's North Hollywood station for booking. Pinner and Rodriguez brought Ledesma, 19, into an interview room and flipped on a tape recorder. Rodriguez read Ledesma his Miranda rights, and Pinner started grilling him. Ledesma, who didn't call a lawyer, showed no signs of cracking. He mocked and swore at Pinner, repeatedly denying any role in the killings.
"You got the wrong person, buddy," Ledesma said.
"OK. I don't agree with you, and I have the evidence to prove it," Pinner said. "I have multiple witnesses who are going to testify that you were the shooter."
Pinner told Ledesma he knew the gang member had been on his way to Martha Puebla's house to visit her the night Vargas was killed outside her house.
To drive home his point, Pinner laid down a "six-pack" -- an array of mug shots that detectives often show to witnesses or victims of crimes. On it, Ledesma's photo was circled, and the initials "M.P." were written below it. "Those is the guy that shot my friends boyfriend" was scrawled along the margin, followed by Puebla's signature.
"I don't even know a Martha," Ledesma lied.
Pinner kept trying, pressing Ledesma about Puebla and the information he said she had given up. At one point he asked Rodriguez for a photo of the girl to show Ledesma. Nothing worked. Ledesma insisted he did not know her.
"Well, she knows you," the detective said.