Members of Suffolk County District Attorney Daniel F. Conley’s Homicide Unit gave closing arguments and opening statements in two unrelated murder trials today, with one case going to a jury and another getting under way.

Assistant District Attorney David Fredette this morning told jurors in the trial of GREGORIO “MIKEY” LOPEZ (D.O.B. 9/3/90) that Lopez had time to contemplate his actions when he shot 32-year-old Shoughan Morgan to death in the early morning of March 11, 2009. Morgan was the ex-boyfriend of Lopez’ girlfriend, in whose Mozart Street home the incident took place; Morgan came to visit that young woman but found Lopez instead, sparking a verbal altercation.

“What did the defendant do?” Fredette asked. “He went out, got a shotgun, he came back to that apartment, walked down the hallway, cool, calm and collected, deliberately and with premeditation opened that door and fired a single shot into the body of Shoughan Morgan.”

Fredette said the defendant did not call 911 or give Morgan warning before shooting the unarmed victim in the torso. “You heard from the medical examiner the different organs that shotgun pellet ripped through, the damage that shotgun pellet did to Shoughan Morgan.”

Fredette told the court that the defendant “had the opportunity and he had the means” to kill Morgan, and more than that, he had the motive. “At one o’clock in the morning, Shoughan Morgan came and woke him up and embarrassed him. That’s the motive – as senseless and sad as it is.”

In a courtroom next door a few hours later, Assistant District Attorney Amy Galatis told jurors what happened between the time 21-year-old John Paul Torres went to a baby shower and the time he died of a stab wound to the chest three days later on May 6, 2009.

After the baby shower, Galatis said, Torres and some friends went to a party at 349 Dudley St. At about 3:45 a.m., a member of his group had words with people associated with RAFAEL LARA (D.O.B. 3/11/91). Lara, a Dorchester resident, was affiliated with a group called DDP, or “Dominicans Don’t Play,” Galatis said.

“It was a stupid, petty argument that escalated to deadly violence,” Galatis told the court. “Mr. Lara grew louder and louder until he reached for a knife … Mr. Lara, knife in hand, swung and hit John Paul Torres in the chest.”

Torres and his group ran down the fire escape into the parking lot, where Torres collapsed, Galatis said. He was rushed to Boston Medical Center, where he underwent emergency surgery but died three days later.

Lara, who was hit in the face with a bottle by one of Torres’ friends trying to pre-empt the stabbing, was approached by Boston Police responding to the scene.

“I got jumped by five black guys,” Lara allegedly told them. After obtaining multiple witness statements and physical evidence, prosecutors approved a warrant for his arrest and the Boston Police Fugitive and Apprehension Unit arrested him June 3, 2009, in New York City.

Lopez is charged with first-degree murder. He is represented by attorney Bruce Carroll. Jurors have retired for the day but will resume deliberations tomorrow morning before Judge Patrick Brady in courtroom 815.

Lara is charged with second-degree murder. He is represented by attorney Martin Leppo. Testimony resumes tomorrow before Judge Diane Kottmeyer in courtroom 817.