Mark Desire estimates that his team had tried to identify the bone half a dozen times over the past 17 years — ever since it was recovered amid the rubble of the World Trade Center in Lower Manhattan. Each time, they came up short.
As part of New York City’s effort to identify the remains of the victims of the Sept. 11, 2001 terror attack, Mr. Desire, the assistant director of forensic biology for the city’s Medical Examiner’s office, and his colleagues had been unable to extract enough DNA from the sample to make a positive identification.
But thanks to advances in DNA testing the team was able to make a breakthrough and on Wednesday the city announced that the remains belonged to Scott Michael Johnson, 26, a financial worker. He is the 1,642 person to be identified of the 2,753 people who were killed in the attack on New York.
Since the destruction of the World Trade Center, the medical examiner has worked to identify nearly 22,000 human remains. Mr. Johnson, who worked on the 89th floor of the south tower as a securities analyst at Keefe, Bruyette, & Woods, is the first victim to be identified since August 2017. The name of the last person to be identified was withheld at his family’s request.
“As a forensic scientist, you’re trained to be neutral and unbiased,” Mr. Desire said. “But with the World Trade Center investigation, it’s a different kind of case and when you meet with the families and the hugs and the thank yous, it gets emotional with them and it really helps with that drive to keep improving that process.”
For Ann and Tom Johnson, the call alerting them to the identification of their son’s remains meant that the medical examiner’s office had kept its promise that it would continue to work to identify victims.
“Having said that, it’s also made me cry and when I told our daughter, we sat there and both cried,” Ms. Johnson said.
She added, “You get pulled right back into it and it also means there’s a finality. Somehow I always thought he would just walk up and say, ‘Here I am. I had amnesia.’”Image Scott Michael Johnson
The Johnsons, who have two additional children, have not planned any services.
Barbara Sampson, the city’s chief medical examiner, who has worked in the office for 20 years and became its leader in 2014, said one of the most gratifying experiences in her career was informing the parents of Patrice Braut, the only Belgian citizen to die in the World Trade Center attack, that her office had identified Mr. Braut’s remains.
“We feel a sacred obligation to continue our work,” she said.
However, the remains that have yet to be identified are the most challenging. Most of the samples are bones, which are some of the most difficult materials to generate DNA profiles from, Mr. Desire said. Compounding the effort is the fact that much of the DNA of Sept. 11 victims was destroyed or degraded because of exposure to fire, heat and jet fuel.
Though the steps for DNA identification have remained mostly the same over the years, the techniques for extracting and identifying DNA samples have improved. First, the bone must be pulverized though recently, Mr. Desire’s team has been able to apply new technology — ultrasonic ball bearings — to this process, which has resulted in a finer powder. The finer the powder, the more DNA that can be extracted, Mr. Desire said.
Then, scientists extract DNA, but because the DNA is often so limited, they try to make copies of it by triggering a polymerase chain reaction using an enzyme. In the case of Mr. Johnson, the scientists performed the process three times before they had enough DNA to create a profile.
Once the DNA profile is generated, the team then compares it to DNA samples. The Medical Examiner’s office has a databank of more than 17,000 reference samples from victims and family members. Mr. Johnson’s DNA sample was compared to a sample from his toothbrush and then confirmed with samples from his parents.
Mr. Desire said the DNA testing techniques have improved in response to the difficulties in identifying 9/11 victims. The DNA crime lab, part of the medical examiner’s office, also conducts research and development, which has been instrumental in technological advancement, Mr. Desire said.
“We are far ahead of where we would have been if not for the necessity of making these identifications,” he said.
For Mr. Johnson’s father, who is a member of the board of the National September 11 Memorial Museum, the identification of his son provides little comfort, he said. Though he said he was grateful that the city had been sensitive and diligent in its work, the news was just another reminder of the pain he and his family have felt for 17 years.
“His friends reported at his memorial service on the incredible love and support that he gave to them that in a sense went even beyond our understanding of him,” Mr. Johnson said about his son. “He was one of the kindest people that anyone around him had ever known. The pain of losing someone like that was tremendous.”
Alain Delaquérière contributed research.A version of this article appears in print on , Section A, Page 21 of the New York edition with the headline: Keeping Its Promise to Families, City Has Identified Another 9/11 Victim. Order Reprints | Today’s Paper | Subscribe