RAY SUAREZ, HOST:
Tomorrow marks 15 years since terrorists killed nearly 3,000 people in the U.S. Most of the victims died at the Twin Towers in New York City, and some 40 percent of those victims are still unidentified. Their families have never received their loved ones' remains. NPR's Hansi Lo Wang reports on the unidentified World Trade Center victims of 9/11.
HANSI LO WANG, BYLINE: Scott Kopytko worked as a commodities broker in the south tower of the World Trade Center, but he quit that job by 9/11 to become a firefighter. He was rushing up the stairs of his old office building trying to save lives with his fellow firefighters before the towers fell.
RUSSELL MERCER: He went to work. He never came back.
WANG: Scott Kopytko's stepfather Russell Mercer and his mother now take turns almost every morning to visit the cemetery across from Scott's old high school. Here under a young oak tree next to fading tombstones, they water pink flowers behind a small square stone engraved for their son.
MERCER: It's a place where we can go, me and my family, to talk to Scott, but there's nothing there. We need some kind of DNA, some human remains where we can go to say this is where Scott is.
WANG: The remains of more than 1,100 other World Trade Center victims are also still unidentified, including those of Sally Regenhard's son Christian, another fallen firefighter.
SALLY REGENHARD: You feel that it's not real. Your mind can't accept the fact that this person died because there's no evidence of it.
WANG: Regenhard keeps a statue of St. Anthony, the patron saint of lost things, by the front door of her home. She remembers how search and rescue efforts at ground zero eventually shifted towards a recovery mission for body parts.
REGENHARD: It was like, you know, being in the rain, in the misty rain and then slowly, slowly as the time went by, you realized it was less and less likely your loved one would be identified.
WANG: New York City's chief medical examiner Barbara Sampson says many the remains were degraded by jet fuel from the hijacked planes and other chemicals released from the collapsed buildings.
BARBARA SAMPSON: There was heat from the fires, water being poured upon them, rain, wind - the worst conditions that you can imagine for the preservation of DNA.
WANG: But the city's chief medical examiner's office was determined.
SAMPSON: We made a commitment to the families to do whatever it takes for as long as it takes.
WANG: That's involved pushing DNA technology to its limits with 10 scientists still dedicated to testing and retesting the remains 15 years after the attacks. Their last new identification was announced last year. But progress on other remains may be held back for years or more because the technology isn't there.
JAY ARONSON: The event itself can never really be put to rest because there will always be remains that can't be identified.
WANG: Jay Aronson is author of "Who Owns The Dead: The Science And Politics Of Death At Ground Zero."
ARONSON: And there's almost this sort of - a very American belief that technology will eventually solve all of our problems.
WANG: But Aronson says this DNA technology raises complicated questions like where should the unidentified remains be stored? For now, they're sealed in plastic bags inside a repository next to the National 9/11 Memorial Museum seven stories below ground. And there's the question of how long to wait for remains to be identified.
MERCER: We'll get him. He'll come back.
WANG: You're hopeful.
MERCER: You have to have it. Once you give up, it's all over.
WANG: Scott Kopytko's stepfather Russell Mercer turned 69 last month. He says if he can't attend a funeral for Scott's remains in his lifetime, then he hopes Scott's sister or even his 2-year-old niece will get the chance. Somebody, he says, will get something. Hansi Lo Wang, NPR News, New York.