(CBS) NEW YORK - Last weekend, police in Long Island identified the skeletal remains of Shannan Gilbert, the New Jersey woman whose May 2010 disappearance led to the discovery of 10 sets of human remains and sparked a hunt for a serial killer who preys on women in the sex industry.
But there has been little apparent movement in the case, and no suspects have been publically identified. One reason could be that medical examiners don't have much to work with.
First, there is the problem of identity: according to the Suffolk County Police Department, including Gilbert's remains, only six of the 11 bodies found along Long Island's beaches have even been identified.
"A homicide investigation is advanced exponentially if you know who the victim is," says Ronal Serpas, the Superintendant of Police in New Orleans.
If the victim's identity is unknown, police can't trace their final movements, talk to their relatives, or determine whether they were involved in activities - like commercial sex work, for example - that might put them at risk for violence. According to Serpas, without an ID, police will search missing person's reports and communicate with other law enforcement agencies. If all that is done and they still don't have an ID, the case goes "in-active."
But even if identity is established - as police were able to do in the case of Shannan Gilbert, who reportedly had a metal plate in her jaw - decomposed or skeletal remains pose major problems for medical examiners who are usually called upon to determine cause of death. Indeed, there is currently disagreement about whether Gilbert was murdered - which her family believes is the case - or drowned accidentally while running through the marshy area, the scenario Suffolk County Police Commissioner Richard Dormer told 48 Hours's Erin Moriarty that he thinks is likely.
According to Dr. Andrew Baker, vice president of the National Association of Medical Examiners and the chief medical examiner in Hennepin County, Minnesota, many of the clues that MEs look for when determining cause of death - from bullet or stab wounds, to cuts and bruises - "simply don't exist anymore" when all you have is a skeleton.
"If the victim was intentionally drowned, or suffocated or strangled, that won't leave marks on the skeleton," says Baker.
Dr. Douglas Ubelaker, a forensic anthropologist with the Smithsonian Institute, agrees.
"The soft tissue holds a lot of clues and if that's gone obviously that's a limitation," says Ubelaker. "It doesn't preclude a determination of cause and manner of death, but it doesn't help."
And when investigators cannot definitively determine cause of death, finding a suspect and convincing a jury of his or her guilt takes on a whole new level of difficulty. Consider the Casey Anthony case: Anthony was acquitted of murder in the death of her 2-year-old daughter Caylee, whose bones were found scattered in the woods approximately six months after she was last seen alive. According to Jeff Ashton, who prosecuted the case, the jury couldn't get past the fact that the state was never able to medically determine the little girl's cause of death.
"I think that was the problem for the jury," Ashton told Crimesider. "They wanted a medical, scientific answer to how she died, not circumstantial."
Ashton says that although they could never tell with scientific certainty how Caylee died, finding duct tape on the little girl's skull indicated to investigators that her death was a homicide. And according to Dr. Baker, when a body is skeletal or decomposed, it is those external clues - clothing, jewelry - that investigators often have to turn to when making conclusions about how the victim died.
"Like any death investigation, the autopsy is just one test we have to interpret who they are, why they were there, and what happened," says Baker.
And although the so-called Long Island Serial Killer case seems to be stalled - on Tuesday, Gilbert's family asked the FBI to intervene in the case after it was reported that police commissioner Dormer and Suffolk County District Attorney Thomas Spota can't even agree on whether the 10 bodies were victims of one or multiple killers - thanks to DNA technology, there is precedent for catching a killer with evidence obtained from skeletal and partial remains.
New Orleans superintendent Serpas was the chief of the Washington State Patrol in 2001 when investigators broke the case of Gary Ridgway, the so-called Green River Killer, who eventually pleaded guilty to murdering 49 women in the 1980s and 1990s.
According to Serpas, the case was made using DNA evidence from bodies that in some cases had degraded over more than 20 years.