A second man, John A. Russo Jr., of Staten Island, was charged with tampering with evidence in Giordano's death and helped New Jersey authorities in the case, said his attorney, George Vomvolakis.
"Based on his cooperation and their own investigation, they were led to this area on Staten Island," Vomvolakis said.
The Mercer County prosecutor's office in New Jersey said the skeletal remains found at the pond Sunday hadn't been identified and DNA testing was being performed.
Giordano, 27, of Hightstown, N.J., vanished in June. Two days later, her 11-month-old son was found abandoned in a hospital parking lot in Newark, Del.
DiGirolamo pleaded guilty in November to reckless endangerment and child abandonment. The child is now in foster care.
DiGirolamo's attorney, Jerome Ballarotto, said they were ready to defend against the murder charge.
DiGirolamo, 33, faces 30 years to life in prison if convicted, prosecutors said. Russo, 43, faces a maximum of 18 months in prison if convicted, they said.
Vomvolakis said Russo would surrender to police in the next few days.
