Rebecca Koster's burning remains were discovered in Connecticut on December 4. Authorities say the 24-year-old's body was wrapped in a blanket, her head in a plastic bag.
Prosecutors say Ganthier cut off her fingers, toes, hair and a tattoo on her back to hide her identity after fatally stabbing her in the stomach.
His lawyer said Ganthier maintains his innocence. A grand jury is reviewing the case.
Koster went missing at 3:30 a.m. after a night out with friends at the Butcher Boys Bar and Grill in Holbrook, Long Island.
Her friends said they dropped her off in front of her home, and that was the last they saw of her.
A series of text messages was made from Koster's cell phone to her family after her death.
Police suspect her murderer sent the chilling and disturbing messages to her family.
The suspect's connection to Koster is not yet known.
Koster had worked as an in-home health aide for autistic children and geriatric patients.