For want of a Glock 9mm with glow-in-the-dark "sights."

That's why a 21-year-old Dorchester man fatally shot three members of a local rap group and their friend, Suffolk County prosecutors charged this week, as the trial of accused killer Calvin Carnes got underway.

But Carnes's attorney, Shannon Frison, said he wasn't at the makeshift recording studio at 43 Bourneside St. that night, and the murder weapons were found on three other people who were never charged and have no connection to Carnes. He had no interest in weapons and there was not any DNA evidence of him being at the scene, she said.

"It's a very tenuous case against him," Frison said, adding that Carnes was crying and shaken when he found out about the murders.

"He lost friends just like the other people," she said, noting that he had recorded a song with the group, Graveside, called "This World." Frison said that one of the victims, 20-year-old Jason Bachiller, was the godfather of Carnes's baby.

The other three victims were Jihad Chankhour, 22, Chris Vieira, the 19-year-old owner of the unregistered gun, and Edwin Duncan, 21, whose lived in the home across from Town Field where the shootings occurred on Dec. 13, 2005.

The murders brought the city's homicide total to 71 in 2005, a ten-year high. It was the city's deadliest shooting incident since 1991.

Carnes, indicted on 11 counts by a Suffolk grand jury, was also after a Mossberg 12-gauge shotgun and an AK-47 rifle, prosecutors said.

"Calvin Carnes decided he wanted that gun and he wanted the other guns," first district attorney Josh Wall said in his opening statement to a jury of 12 members and four alternates. "That's when he took the Glock and shot and killed Chris Vieira."

The other three were shot because they were witnesses, Wall said.

The group used the guns as props, prosecutors said, and Vieira would often show off his recently obtained handgun.

Jelani Haynes, a friend and a producer with Graveside, said the basement, complete with a bar, was often used as a gathering place for the social circle, with people there playing video games on an Xbox and Playstation 2, drinking alcohol, and smoking cigarettes and marijuana. The group had not gained any notoriety at the time, he said.

"We did not have any vendettas, disputes," he told the jury.

Haynes recalled that Vieira had sometimes shown off the Glock. "He was treating it like a show-and-tell," he said.

Wall, the prosecutor, said that after shooting the four men that December night, Carnes took Vieira's car keys and ran from the scene with Robert Turner, his best friend, later attempting to hide the weapons and create alibis.

Turner, charged as an accessory after the fact to the murders, pleaded guilty to all charges last month and received a 13-year sentence in state prison.

Frison, Carnes's attorney, said Carnes was elsewhere in Dorchester that night, and learned about the murders on the news.

A man matching Carnes in height, weight and build was seen running from the basement and getting into Vieira's car in front of the Bourneside home, according to prosecutors. Carnes left behind fingerprints in the basement and Vieira's car, they add. Police found Vieira's car, with the keys in the ignition, on a Dorchester street near the home of one of the Turner's relatives.

Darnella Phillips, Duncan's mother, had heard the gunshots and attempted to call her son's cell phone. From a window, she saw a lone man approaching Vieira's car.

"I went down to the basement, and that's when I saw my son and Jason lying in front of the stairs. Jason's body was completely riddled with bullets. My son was lying there lifeless," she told the jury, according to Suffolk County Distirct Attorney Dan Conley's office.

The trial is expected to last four to six weeks.

The special grand jury, which lasted from March through July in 2006, saw 60 witnesses appear before them and over 90 physical exhibits, including photographs, and medical and forensic reports.