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A Carnegie Mellon University graduate is the latest victim whose remains have been identified in the 2001 World Trade Center attacks, moving the New York medical examiner’s office one step closer to its ultimate goal of putting a name to all of the tissue samples it has kept for years.
Matthew David Yarnell, a young New Jersey computer analyst who graduated from Carnegie Mellon University in 1997, was positively identified last week, said his mother, Michele Yarnell.
At this point, only about 60 percent of the World Trade Center remains have been identified, and many forensic experts believe it will be impossible to put a name to all of them. Still, new techniques are slowly adding verifications like Yarnell’s.
Just a year ago, medical examiner’s officials had told the family that tests had failed to find a match, Michele Yarnell said, but last week, they told her new techniques had yielded a success.
For her, the news carried no special emotional impact. “It hasn’t really changed anything. I still have the same feelings. We didn’t expect any different result. We knew that he was gone.”
While the examiner’s office would not comment on the specific tests used on Yarnell’s remains, forensic experts said the catastrophe had led to several new tools to make it easier to identify damaged tissue samples.
John Butler, a special assistant to the director of forensic science at the National Institute of Standards and Technology, said there have been four key developments in the 14 years since the Sept. 11, 2001, attacks.
First, researchers have figured out how to extract more DNA from bone samples. Where scientists used to grind up the bone, they now use a special chemical solution to dissolve it.
They also have learned how to use smaller stretches of DNA to hunt for unique markers. One key technique involves hunting for repeated sequences of nucleotides, the chemical subunits that make up DNA. A victim and his family members will often have a certain number of those repeats.
Years ago, scientists needed a stretch of 200 to 300 nucleotides to look for repeat sequences, Butler said, but his office helped develop a technique that allows them to use just 100 or so nucleotides, meaning they can hunt for identification using much smaller samples.
Forensic scientists compare the remains to known samples of DNA from the victim or from close relatives. In Yarnell’s case, the family provided the examiner’s office with a comb and toothbrush from his apartment, as well as blood samples from his mother, father and siblings.
The identity sleuths also use a chemical technique to amplify the amount of DNA in a sample. Remains damaged by fire or water, like those at the World Trade Center, often interrupted that amplification process, he said, but new chemical buffers have overcome that obstacle.
Finally, new software has been developed to virtually reassemble the pieces of DNA into a whole sequence, he said, further increasing the odds of a successful identification.
Forensic pathologist Judy Melinek, who got her training in the New York medical examiner’s before and after the 9/11 attacks, recalled that “the forces at work during the World Trade Center disaster included explosions, blunt trauma and fire. Then, after the collapse, fire suppression efforts introduced water and many remains were not recovered for months. The combination of heat, water and decomposition made identification very challenging, and that is why DNA has been used.”
New tools in the future may allow more identifications, and “this may help bring closure to some victims’ family members,” said Melinek, who wrote about her New York training in the book, “Working Stiff: Two Years, 262 Bodies and the Making of a Medical Examiner.”
Saturday 21 March 2015
http://readingeagle.com/ap/article/remains-of-carnegie-mellon-grad-911-victim-at-world-trade-center-are-identified
