Image source, Juliette ScausoImage caption, Juliette Scauso was four, the youngest of four children, when her father, firefighter Dennis Scauso, was killed in 9/11
For 25 years, the only physical trace Juliette Scauso had from the last day of her father's life was his mangled firefighter helmet.
Scauso's father, Dennis - part of a New York City Fire Department (FDNY) hazmat unit for 12 years - initially was not scheduled to work on 11 September, 2001, but switched shifts for the overtime pay.
The Long Island father of four was likely in the South Tower of the World Trade Center when it collapsed, the Scauso family was told. The helmet with his badge number was found months later.
"I've spent essentially my entire life knowing my father died, and learning to live with the fact that we never recovered him," said Scauso, who was four when he died.
Dennis Scauso is one of more than 1,000 people killed on September 11 in New York who have yet to be identified, according to New York City's Office of Chief Medical Examiner. Nearly 3,000 people died in the World Trade Center attacks that day.
Last month, the city announced the identity of a previously unknown victim of the terrorist attacks - the 1,654th person - using a new technology called forensic investigative genetic genealogy - or FIGG.
"There is real promise in using this approach," said Angela Soler, director of forensic anthropology in the city's medical examiner office. "There's hope for more families to receive answers, and hopefully we'll be able to test more remains in the future using this technology as well."
Since 9/11, Soler's office has sought to identify the remains of the 2,753 victims who died in the World Trade Center. So far, 60 percent of those killed have been identified.
"It's been one of the most complex identification efforts that I think anybody has ever really experienced," Soler said.
Efforts to identify victims have been complicated by a number of factors.
Human remains were damaged in the plane crashes and fires caused by jet fuel, meaning the office had only portions of victims for DNA samples, Soler said.
Scauso added that because of the timing of the attacks, many firefighters were changing shifts, but some stayed to help, grabbing whatever extra gear they could find. This meant some first responders recovered were wearing uniforms with others' names, complicating identification.
The World Trade Center site also had many more victims than the other 9/11 terrorist attack sites.
The remains of five of the 184 people killed when American Airlines Flight 77 crashed into the Pentagon were never identified because of similar conditions. According to the National Park Service, enough remains were recovered to use DNA, dental records and fingerprints to identify all 40 victims aboard United Airlines flight 93, which crashed into a field in Shanksville, Pennsylvania.
Remains from the World Trade Center have been packaged and sealed to help preserve DNA for testing in the years to come. Soon after the attacks, individuals were identified using fingerprints or dental records, but as time went on, when neither was available, the office turned to DNA. Officials were able to use new technology to extract DNA and retest the same remains.
"That's why all these years down the road, we're still getting new identifications, because we're just continuing to retest and retry with every new technology that becomes available," Soler said.
DNA technology has helped the office identify 1,495 victims since 9/11 - some solely with DNA and others with multiple methods - according to the medical examiner's office.
Last year, the city announced that with the help of DNA, 24 years later, it had identified three new victims - Ryan Fitzgerald, a 26-year-old currency trader, Babara Keating, a 72-year-old who was aboard American Airlines Flight 11 from Boston to Los Angeles, and a woman whose family kept her identity private.
Soler said the new FIGG technology uses whole genome sequencing - which provides a way to read someone's entire genetic code. It means investigators can make more potential matches to family members who are more distant relatives of the victim. Once those matches are made, the New York Police Department helps find relatives who are closer to the victims.
The medical examiner's office in New York still gets weekly calls from loved ones asking about someone whose remains were never recovered.
Many have never been able to bury a loved one, but some families choose to leave the remains - once found - at a repository at the 9/11 memorial site in New York. The repository was built into the bedrock of the World Trade Center site and can only be accessed by medical examiner staff. A nearby private space, known as the reflection room, is available for families to mourn.
"That's where their loved one was in their last moments, and that's where they want them to stay", Soler said.
Some don't want to be notified, perhaps because the confirmation is too painful, said Soler, who helps inform families.
Scauso is one of those people. She knows people who, in recent years, got a call that a relative finally has been identified. The thought of being next on the list is scary for her family, who has worked hard to keep the memory of her father - a jack of all trades and a lover of jazz - alive.
"At this point, an identification wouldn't change the reality of his death. It wouldn't give me back my father, and I don't necessarily want to reopen something that has become part of the way I've learned to live and grieve," she said. "Especially 25 years later, it's going to open up the wounds again."
Image source, Juliette ScausoImage caption, Scauso says that her father Dennis's helmet was the only item recovered, with his FDNY badge, where he worked for 12 years
Soler has seen the news provide a mix of both relief and sadness. "It's confirmation of something that they always knew to be true - they knew their loved one died on 9/11, but I think for many families, there's still that question in the back of their mind until the remains are formally identified," Soler said.
"Maybe they're reliving it a little bit more now, having this new identification. But at the same time, it closes one chapter of their journey after 9/11," she added.
To Soler - and some of her current colleagues who also were on the ground during 9/11 - the work is deeply personal. Workers from their office arrived at Ground Zero after the planes hit the towers, and were there when the buildings collapsed.
They are aware it is unlikely they will identify every victim of the New York attacks. In some instances, there may be no remains of a victim at all. Still, they have no plans to stop.
"As long as there's families looking for answers, we'll continue searching for them," she said.
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