Suffolk County District Attorney Daniel F. Conley today named Assistant District Attorney John P. Pappas as his new chief trial counsel, making the longtime homicide prosecutor the senior strategist in litigating more than 40,000 criminal cases per year in Boston, Chelsea, Revere, and Winthrop.

“John Pappas exemplifies the qualities I look for in a prosecutor,” Conley said of the lifelong Boston resident. “He’s fair, honest, and team-oriented. He has an exceptional command of criminal law and has excelled in every position he’s held throughout almost 20 years of public service.”

Pappas, 46, began his career as a prosecutor in 1994 as a line assistant district attorney in the Boston Municipal Court and went on to be the supervising ADA in East Boston District Court. In 1997, he was promoted to a Superior Court trial team then known as the General Felony Unit, with subsequent placements in the Gang Unit, Senior Trial Unit, and Homicide Unit. Pappas replaces former Chief Trial Counsel Patrick Haggan, whom Conley named his first assistant earlier this year.

As chief trial counsel, Pappas assumes a position on the DA’s executive staff, where he will provide legal and tactical guidance to Superior Court trial teams in investigative, grand jury, and trial matters. He will continue to shoulder a full caseload of homicides and death investigations.

“I want to express my deep appreciation to District Attorney Conley for appointing me to the position of chief trial counsel,” Pappas said. “I am both humbled and honored by the appointment. I welcome the help and support of so many colleagues – assistant district attorneys, victim-witness advocates, civilian investigators, and administrative staff – who together work tirelessly to protect the citizens of Suffolk County with justice, integrity, and fairness.”

In recent years, Pappas has prosecuted the executions of Julio Ceus and Natalie Sumner during a robbery in a Brighton apartment; the murder of 16-year-old DeAndre Barboza on a Dorchester street corner; and the assassination of 15-year-old Soheil Turner as the boy waited for a bus to school. The defendants in those cases were all convicted of first-degree murder and are serving life in prison without the possibility of parole.

As a gang prosecutor, Pappas secured convictions against two men in connection with the 2000 stabbing of Boston Celtics player Paul Pierce in a downtown nightclub, even when the victim and multiple witnesses recanted their previous identifications of the assailants. Those convictions were later upheld by the Massachusetts Appeals Court.

Pappas also directed the investigations into the fatal shootings of Jay Carciero, slain by an off-duty special police officer as Carciero stabbed a doctor at a Staniford Street clinic, and Marquis Barker, who stole a cruiser and pointed a replica handgun at Boston Police officers responding to multiple 911 calls for a man with a gun. Neither case resulted in criminal charges.

“Through each of these cases and so many more, John demonstrated a steady hand, an unwavering persistence, and the highest levels of preparation,” Conley said. “He’s earned the respect of judges, police, defense attorneys, his own colleagues, and, most importantly, the victims and families he’s served.”