A three-judge appeals court panel ruled in August that the statement made by Gerardo Gomez was not admissible because he wasn't adequately informed of his Miranda rights.
The Essex County Prosecutor's Office appealed, saying Gomez "knowingly and voluntarily waived his right to remain silent."
The 18-year-old Gomez is one of six defendants in the case. One has been convicted; another has pleaded guilty. The others are awaiting trial.
The prosecutor's office said Monday it will move forward with the case, relying on other evidence.