Who is the Gilgo Beach serial killer?

Shannan Gilbert was finally laid to rest after nearly five years. Her family now hopes a new autopsy will yield answers about her death.

Her disappearance led to the discovery of a mass grave of women -- all sex workers in their 20s -- all strangled by a suspected serial killer.

But police say they're unable to determine how Gilbert, a 23 year old escort, died. They've speculated she drowned in the marsh where she was found.

There's enough evidence to warrant a second look.

Now renowned forensic pathologist Dr. Michael Baden has taken on the case. He believes it's highly possible Gilbert was strangled.

An autopsy of her remains this week - shot exclusively by Fox - showed roughness on one side of the hyoid bone - a bone in the neck at the top of the voice box. With the permission of the family, Baden is conducting further testing.

"If it is a fracture that would be strong evidence that this young lady was strangled to death by neck compression and changes it from undetermined to homicide" Dr. Baden said.

Officials say there is no doubt that victim Shannan Gilbert was murdered.

Gilbert was last seen by a client, Joseph Brewer, who hired her that evening. He maintains his innocence.

Attorney John Ray who represents the Gilbert family, believes Shannan ran from Brewer's home and fell into the hands of his neighbor, Charles Peter Hackett -- a doctor who some say has shown a strange interest in her disappearance.

Phone records show Hackett called Gilbert's mother two days after she disappeared. A year and a half later, her body was found yards from his home, near the same area as the other women.

Unlike the other victims, police know who Gilbert was with that night. If it's proven she was murdered, is could change the course of the investigation into all the deaths.