Along with three murder counts, Alfaro faces robbery, attempted murder and weapons counts. Prosecutors allege Alfaro used a machete to attack 20-year-old Iofemi Hightower, one of the victims.
A judge ruled last month that Alfaro can be tried as an adult. Two other suspects who were 15 at the time of the killings are undergoing evaluations to determine whether they can be tried as adults as well.
Alfaro and the other juveniles pleaded not guilty in their initial appearances in juvenile court, which is closed to the public, according to the Essex County Prosecutor's Office. The Wednesday hearing was Alfaro's first appearance as an adult.
State Superior Court Judge Donald J. Volkert Jr. kept Alfaro's bail at $1 million, pending a motion by prosecutors to have the bail raised to $4 million.
Alfaro is the half-brother of another suspect, Rodolfo Godinez. The two were arrested within an hour of each other in Virginia and Maryland, respectively, two weeks after the August slayings.
Alfaro, Godinez and four others are accused of murdering Hightower, 18-year-old Terrance Aeriel and 20-year-old Dashon Harvey on the night of Aug. 4 in a playground behind the Mount Vernon School. The three victims were ordered to kneel against a wall and were each shot in the head.
Aeriel's sister, Natasha, survived a gunshot wound to the head and was able to help authorities identify some of the suspects. She and her family are living at an undisclosed location under the custody of the state's witness protection program.
The Aeriels and Harvey were students at Delaware State University, while Hightower was in the process of enrolling for the fall semester.
