One of Thomas Webb’s last living acts was to pet a dog in the company of his friends, a Suffolk County homicide prosecutor told a Superior Court jury today.

Assistant District Attorney David Fredette of DA Daniel F. Conley’s Homicide Unit said Webb, 17, was killed in front of 923 Parker St. on the night of Sept. 15, 2008, and that ELBERT NEWSON (D.O.B. 12/9/88) was one of the men responsible.

“This person, Mr. Elbert Newson, was one of two people who shot and killed Mr. Webb,” Fredette said. “But what he didn’t know was that just up the street there were a couple of Boston Police officers in a marked police car.”

Delivering his opening statement in Newson’s trial for first-degree murder and unlawfully possessing both a .45 caliber semiautomatic handgun and a .38 caliber revolver, Fredette said the nearby officers heard the sound of two separate guns being fired and sped toward that sound to find a dark grey Nissan Maxima near the intersection of Heath and Parker streets.

The officers saw someone running into that car, which had its lights on and engine running, Fredette said, and they tried to box it in.

“The driver evaded them, drove around them, and led them on a high-speed chase,” the prosecutor told the court.

Thirty seconds into the chase, the officers saw an item – later found to be a .45 caliber handgun – tossed from the passenger’s side window. They never lost sight of the car as it drove toward the Academy Homes housing development. The car stopped, the passenger ran into the projects, and the driver ran toward Dimock Street.

Newson, whom prosecutors say was the driver, was apprehended on Notre Dame Street. Sweating and out of breath, he allegedly denied driving the car; Fredette said he had its key in his pocket when he was taken into custody. A second handgun found on the car’s front passenger seat had Newson’s fingerprint on it, he said.

“The evidence is going to prove that Elbert Newson knowingly participated in a meaningful way in the murder of Mr. Webb,” Fredette said, noting that he didn’t expect witness testimony to establish who pulled the trigger.

“You’re going to hear that the people out there that night didn’t see whole lot,” he said. “No one said, ‘Hey, someone is going to show up in a couple of minutes and shoot Mr. Webb, so pay attention.’”

Katherine Moran is the DA’s victim-witness advocate assigned to the case. Newson is represented by attorney Stephen Neyman. Testimony is ongoing before Judge Christine McEvoy in courtroom 808 of Suffolk Superior Court.