Assistant District Attorney Brian Zarallo told the jury of seven women and five men that the evidence would show that DiPietro, 50, was "executed in the street" by an assailant who is still at large, and that Nicodemo's job was to help him escape and ditch the weapon.
Zarallo said the evidence would be sufficient to find Nicodemo guilty of first-degree murder and conspiracy to commit first-degree murder.
"One thing I cannot answer is why," Zarallo said. "I wish we could, but there are certain things people hold within their hearts and within their heads. And one thing the commonwealth doesn't have to prove is motive."
In his opening, defense attorney Brian J. McMonagle portrayed Nicodemo as the victim of an aborted carjacking.
McMonagle said Nicodemo was driving his black Honda Pilot SUV when a masked, gloved gunman jumped into his car. As Nicodemo drove, the man reached behind him and stashed the murder weapon in a pocket at the rear of the driver's seat, then jumped out and ran.
"He had no idea what had just hit him," McMonagle said.
McMonagle ridiculed the idea that Nicodemo was part of a conspiracy to kill DiPietro: "Why would he drive his own car in a neighborhood he had lived every day for years and where everyone knew him, and commit this crime?"
DiPietro, who had served time for drug dealing, was gunned down in the 2800 block of South Iseminger Street shortly before 3 p.m. Dec. 12, 2012, as he stood next to his gold Mazda pickup truck, which was parked near his home.
Among the trial's first witnesses was James Noone, who had delivered mail on that route for 20 years and said he knew DiPietro.
Noone said he had parked his mail truck in the 1200 block of Johnston Street when he heard a shot. He said he walked around the corner and looked down Iseminger, where he saw a masked man standing over the body of a man near a gold pickup, firing rounds into him.
Another witness, Louis Houck, said he was walking along South Camac Street when he heard four or five shots and saw a masked man run south from an alley and jump into the back of a black Honda Pilot. He said he memorized the tag number, HTK-1942, and reported the information to police arriving at the scene.
Zarallo said that within minutes, police had identified the vehicle and were at Nicodemo's house in the 3200 block of South 17th Street, where he was taken into custody.
Zarallo said a .357 Magnum revolver was found wrapped in clothing in the back of the driver's seat. Zarallo said ballistics tests showed the revolver fired the shots that killed DiPietro.