MAFIA HITS? A serial killer? Perhaps a boating accident?

Imaginations can run wild, particularly when two human legs have washed up in the Delaware River and what appeared to be a human finger was found at the Jersey Shore.

Investigators have to fight that urge, though, and grapple with a frustrating set of facts that mandate hundreds of phone calls, sorting through reams of old case files and DNA databases, and knocking on doors of families unhinged by the unknown.

"First, we have to get the ID, and then we can start thinking about the investigation," said Det. Sgt. John Donegan, 41, of the New Jersey State Police Missing Persons Unit. "It's definitely not 'CSI.' They solve a homicide and get a conviction in a half-hour show. This is pretty complicated."

Ultimately, as in the case of the severed leg found May 24 in the Delaware River in West Deptford, Gloucester County, months of work can yield no answers.

This is what the New Jersey State Police Missing Persons Unit has to work with: The leg was severed cleanly below the knee with a small patch of skin cut out from the ankle, but with no other internal or external injuries. The leg was fresh, Donegan said, only in the water for a few days, and belonged to a white female between 5 feet 1 and 5 feet 5 inches tall. The woman wore a size 5 1/2 shoe and her toenails appeared to have been removed.

Calls were made to hospitals, morgues and police departments in New Jersey, Pennsylvania, Delaware and New York in an effort to match the leg with a body. They also entered DNA from the leg into CODIS, the FBI's national database.

"You have some scenarios running around your head, sure, but until you know who it is, you cannot proceed with any criminal investigation," said Detective Glenn Garrels, of the New Jersey State Police major-crimes unit. "We would have hoped to have found a body, but it hasn't shown up. You can't even narrow it down anymore."

Neither Donegan or Garrels - who would investigate if the leg had been involved in a crime - would speculate on whether the woman had been murdered, the victim of an accident or a suicide, they said, because there's always the unlikely possibility that she may not be dead.

"Could it have been medical waste? I would like to think it couldn't, but I can't rule anything out," said Donegan, a 15-year veteran of the force.

A little more than a month after the leg appeared in West Deptford, investigators with the missing-persons unit contacted Easton, Pa., police after a fisherman there discovered another human leg in the Delaware River. It wasn't the break they had been hoping for.

"It had a different foot size," Donegan said.

The body parts kept coming, though. At least, that's how it appeared July 30, when police were called to a home in Brielle, Monmouth County, after a homeowner discovered what appeared to be a severed human finger, complete with a French-manicured fingernail, on the deck.

Investigators first believed a seagull had dropped the finger from above, and that it may have been associated with 72-year-old Julia Madsen, a woman suffering from Alzheimer's disease who went missing in June while walking on a beach in Berkeley Township, Ocean County.

Then things got weird. Initially, the Monmouth County Medical Examiner's Office couldn't determine whether the finger was human, and eventually a forensic anthropologist X-rayed it, found no bones, and determined it was made of an unidentified substance.

"We don't know what it was," Donegan said, adding that the specimen was destroyed.

After potential leads in two different regions of the state dried up, the West Deptford leg seemed destined for a cold-case file.

But in March 2008, New Jersey missing-persons investigators and families of people missing across the Garden State gained a high-tech friend in Texas.

Under Patricia's Law, legislation named after a Bergen County county woman missing since 2001, New Jersey now would seek DNA samples from unidentified bodies and relatives of the missing that would be analyzed at the University of North Texas Center for Human Identification.

George Adams, the center's program coordinator, said that New Jersey has been the model agency for the program and that he believes that the long-term results will be impressive once more families of the missing submit DNA.

"You should never have a cold case anymore," Adams said of unidentified persons.

It's not a matter of pressing a button on a computer, though. Finding a match could take months, Adams said, or even longer.

"We will not give a time frame," he said, noting that the program adds no extra cost to law enforcement.

Donegan said that the program had its first match last month, when the DNA program helped to positively identify a body in New York City as 17-year-old Ben Maurer, missing since 2001 from his home in Piscataway, Middlesex County.

Donegan is hoping that the partnership with Texas will break another case, involving the skeletal remains of a black male found on New Year's Eve 2008 along the shore of the Delaware River in Greenwich Township, Gloucester County.

Investigators believe that the man, wearing a shirt with the word "Maine" across the front, had drowned, but they don't know how.

"There's a variety of ways someone could wind up in the water," Donegan said.

Hundreds of potential matches came up for the man among missing persons, and one by one, Donegan has been crossing them out.

Cases that seem ripe with evidence, such as the unidentified female found stuffed in a U.S. Mail bag in the Delaware River near Pennsauken in 1996, have yielded no results. That woman had extensive dental work, an orthopedic screw in a toe and a ring with "Avon C" inscribed on it.

"You can't tell me there's not someone out there who doesn't know she's missing," Donegan said.

On the other end of the spectrum are identified missing people who haven't been found, which as of July numbered 1,212 in New Jersey. An additional 300 bodies or body parts remain unidentified, authorities said.

Many are runaways, prostitutes, elderly suffering from various states of dementia or Alzheimer's and children taken to other countries by a parent. Many of the pictures are posted on the State Police Web site, smiling in happier times.

Their cases often require the missing-persons unit to contact other countries, in one case requesting fingerprints from Poland and, in the case of Stephen Davaris, sending dental records to Ireland.

A relative last saw Davaris in Secaucus, Hudson County, on July 6, 2005, and he turned up in Ireland two days later. Officers there said that he was last seen in a pub, and his passport and mobile phone were found washed up on a County Clare beach on July 13, 2005.

Missing people are found, often alive and well amid tearful celebration. Confirming the identity of a body or body part is a joyless victory, a simple confirmation of a family's worst fears - if there is family - and moves investigators one step closer to writing the final chapter of a life.

"It's a necessary evil, but you bring some closure to the family with an ID," Donegan said. "You don't feel good about anything."

Tipsters can contact the New Jersey State Police at 800-709-7090.