Jessica Nunez was screaming on the sidewalk.

The plainclothes cop who was the first to respond to a report of a "person shot" at 50th and Parrish Streets saw the hysterical teenager and knew something terrible had happened.

Detective Matthew Carey ran into tiny Lorena's Grocery, gun drawn, he told a courtroom Tuesday. Near the front of the store, he found Porfirio Nunez, Jessica's father, lying motionless. There was a trail of blood leading to the back of the store.

On the floor near the deli counter, he found Lina Sanchez, Jessica's aunt, and Juana Nunez, Jessica's mother, blood pooling around them. One of the women, Carey said - "I'll never forget this" - had wedged herself into a small space between the lunchmeat counter and the refrigerator, as if in a last, desperate try to escape her attackers.

All three had been shot dead, Jessica and her sister Laura would later tell police, by a pair of robbers who made off with a few hundred dollars in cash, and in the process destroyed a family.

On Tuesday, more than five years after the murders took place, a jury heard opening arguments in the case of Ibrahim Muhammed and Nalik Scott, who face the death penalty if convicted of the killings.

Prosecutors say dogged police work and sharp-eyed investigators led them to Muhammed, who confessed after he was arrested in February 2012, several months after the murders, on an unrelated drug charge.

"He told [detectives] things only the killer would know," prosecutor Kirk Handrich said.

Defense attorneys Larry Krasner and Jack McMahon contend that their clients are innocent and that the case against them is based on mistaken identity, faulty identifications, and a false confession - taken while Muhammed, who is schizophrenic, was off his medication.

Krasner called the case "a bottomless well of misery, pain, suffering, and trauma." But he said there was "only one thing worse" than what the Nunez sisters went through - "and that's convicting innocent men and letting the killer go free."

The Nunez sisters, who prosecutors said looked their parents' killers in the eye during the rampage in the store, are set to testify this week.

"There are some things a robber cannot take and a killer cannot snuff out," Handrich said. "They cannot take away the courage to face the people who took away their family."

Jessica Nunez, Handrick said, spent the months after the murders working at a number of bodegas in the neighborhood, hoping her parents' killers would turn up.

Once, a man walked into one of the bodegas who looked so like the gunman that Jessica, who had been working the cash register, fainted. This was an example of her commitment to finding justice, Handrich suggested.

Krasner countered that the man Jessica Nunez encountered in the bodega - who was caught on video and identified by police as a member of a local crime ring - could be the real killer, and that investigators had dropped that lead after Muhammed confessed.

"This is a case of misidentification," said McMahon, who is representing Scott. "I don't doubt [the Nunez sisters'] belief. I doubt their accuracy."

The sisters' initial descriptions of the murderers did not match their clients, Krasner and McMahon said.

That afternoon, the girls' family members sobbed quietly during a crime-scene investigator's testimony. Prosecutors showed photos of the bodega's bloodstained floors and bullets lodged in the walls. One bullet was found in a block of cheese, and crime-scene investigators picked nine spent shell casings from the floors.

Porfirio Nunez, who emigrated from the Dominican Republic 20 years ago, had bought the bodega and worked hard to bring his family members to Philadelphia, prosecutors said. He taped family photos to the front counter and had been planning to celebrate his birthday with his daughters the night he was killed.

"Instead, these young girls walked out of that store orphans," Handrich said. "The weight of the world was dropped on them in just a couple minutes."

The trial is set to continue Wednesday. Prosecutors say they expect to rest their case sometime Thursday.

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