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Taking Measure

Just a Standard Blog

Reflections on Assisting With the 9/11 World Trade Center DNA Identifications

collage of images from the WTC disaster and the NYC skyline with a representation of a DNA molecule and the letters DNA,
Credit: N. Hanacek/NIST

On Tuesday, Sept. 11, 2001, I walked to work from my home in Olde Towne Gaithersburg, Maryland, and arrived at my office shortly before 9 a.m. I had just returned from an International Society for Forensic Genetics meeting in Germany where I had spoken on a new DNA test our NIST team had developed. My task that morning was to prepare some samples in our laboratory of this new DNA test to ship to our collaborators in the New York City Office of Chief Medical Examiner (NYC OCME) Forensic Biology Laboratory.

However, these particular samples were never sent, as the attention of the NYC OCME — and the rest of the world — moved to the aftermath of the events on that fateful morning.

DNA Identification Efforts

Terrorists hijacked and crashed four passenger airplanes on 9/11 (one into each of the World Trade Center twin towers in New York City, one into the Pentagon in Washington, D.C., and one into a field near Shanksville, Pennsylvania). This tragedy took the lives of all those aboard these planes as well as many people in the Pentagon and the World Trade Center twin towers that collapsed in New York City. In total, almost 3,000 people died that day.

Returning remains of loved ones to their families is important — and depending on the circumstances can be challenging. The International Committee of the Red Cross has noted: “The proper recovery and identification of human remains is … a fundamental part of the healing process for families and even whole communities.”

Human identification following mass fatality incidents involves comparing antemortem records with postmortem information. Intact bodies may be identified visually by dental records or fingerprints. Death certificates can then be issued and remains returned to surviving family members. DNA is a method of last resort in mass fatality identification efforts because it takes longer and is more expensive than other means.

Due to the fragmentation of bodies that occurs with high-velocity plane crashes and building collapses, DNA became a primary means of identifying many of the remains recovered from 9/11. This identification effort took place in multiple forensic DNA laboratories and over the course of several years. Remains recovered from the Pentagon and Shanksville crash sites were processed fairly quickly. The World Trade Center (WTC) remains took months to recover from the site and much longer to process because of the numbers of samples and condition of the remains.

DNA identification requires recovering a DNA profile from a piece of tissue or bone and having a reference sample to compare — either a direct reference sample from the disaster victim (such as from a toothbrush or item of clothing recovered from their home) or a kinship sample from a close biological relative (such as a parent or child who is expected to share a portion of their DNA).

For the WTC site, which is probably the largest forensic case in history, new methods had to be developed and software deployed to correlate DNA information between the remains recovered and reference samples obtained from families of victims. The WTC site conditions left DNA molecules from surviving samples badly damaged and fragmented. You can think of DNA fragmentation like recovering only a few digits from a phone number and not having enough information to make the call.

My involvement in the WTC DNA identification efforts began several months after 9/11 when it became apparent that extraordinary efforts were needed to complete many of these DNA identifications.

Creation of New DNA Tests

In early October 2001, Lisa Forman from the National Institute of Justice (NIJ), the research arm of the Department of Justice, which was at the time funding our work at NIST, called to tell me that she had volunteered my services to NYC to help them with their DNA identification efforts. A few weeks later, Robert Shaler, the NYC OCME laboratory director who directed the DNA identifications, called and asked if I would help design new DNA tests to improve recovery of information from highly fragmented samples with degraded DNA. Shaler had seen a presentation I had given at a conference and knew that I had performed some research on reducing the size of short tandem repeat (STR) markers used in DNA tests.

In fact, a few years earlier, I had, perhaps somewhat prophetically, written in a research article that the work we were doing could be useful for potential forensic situations with degraded DNA.

I wrote in my journal the night Shaler called: “I hope [this new DNA test] will help identify some of the victims from the World Trade Center disaster.” This thought motivated me to action as perhaps never before in my career. Here was a chance to make an impact on an important ongoing effort!

I spent many late nights at NIST throughout December 2001 and January 2002 developing what I termed “miniSTR” DNA tests and preparing materials for assessment by the NYC OCME DNA laboratory.

The real question was whether these new DNA tests would help recover more genetic information from badly damaged samples. We could prepare a new DNA test, but the true value could only be known by using it with burned bone and tissue samples, something that would need to be done in their laboratory. Thus, materials had to be prepared and packaged, software macros and protocols written, and validation experiments performed.

We regularly shared our progress with Shaler and his colleagues. They decided to focus on one of the new tests, which we named the “Big Mini.” Shaler later wrote about this test in chapter 12 of his 2005 book Who They Were: Inside the World Trade Center DNA Story: The Unprecedented Effort to Identify the Missing.

The initial test showed promise but needed further modifications before it was ready for prime time. Before long, thousands of DNA samples were being tested by Bode Technology, a laboratory under contract with NYC OCME, using modified versions of the miniSTR tests developed at NIST — and new genetic information was recovered from the badly damaged human remains at the WTC site.

Shaler later told me that more than 20% of the identifications they made came from miniSTR results.

World Trade Center Kinship and Data Analysis Panel

Obtaining DNA results from recovered human remains was only part of the challenge of 9/11. No one had ever attempted to correlate so many human remains with so many families before. The scale for the WTC DNA identifications was orders of magnitude more challenging than an airplane crash. In addition, involvement of multiple agencies in sample collection led to a proliferation of labels for the same sample.

Shaler and his NYC OCME team sought assistance and advice from an expert panel regarding the many issues that arose following 9/11. NIJ gathered a group of about 30 eminent scientists from across the federal government, academia and private industry to assist the NYC OCME in their DNA identification efforts. NIJ funded bimonthly meetings for this World Trade Center Kinship and Data Analysis Panel (WTC KADAP).

The efforts of WTC KADAP were later described in a Science article, of which I was privileged to be a co-author. NIJ also published lessons learned from our WTC KADAP experience in “Lessons Learned from 9/11: DNA Identification in Mass Fatality Incidents” to assist in future efforts.

Progression of Science and Impact on My Career

Progress can spring from tragedy. Valuable collaborations came from united efforts in assisting with the 9/11 DNA identifications. New technologies were developed. Our miniSTR efforts would later be used in future commercial DNA testing kits — and these DNA tests have assisted in many other investigations containing challenging samples, including identifying the remains of the Romanov family almost a century after they were killed and reconstructing the ancestry of ancient Egyptian pharaohs from 3,000-year-old mummies in King Tut’s lineage.

Because of experiences gained with WTC KADAP, I participated in efforts to identify victims following Hurricane Katrina in August 2005. I was also invited to Geneva, Switzerland, in May 2008 to assist the International Committee of the Red Cross in considering DNA identification efforts with mass fatality incidents that it encounters. Thus, what began as a simple phone call from a scientific colleague in need in November 2001 has led to interactions with efforts around the globe.

NIST's World Trade Center Investigations
NIST's World Trade Center Investigations
Learn more about NIST's work on the World Trade Center investigations, from how it conducted the study to the recommendations and their lasting legacy. Visit

About the author

John Butler

John Butler is a NIST Fellow and special assistant to the director for forensic science. He is a leading expert in DNA and has written textbooks on DNA typing methodology and interpretation. Through DNA testing, he has also shown that he is the father of his six children.

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When will the NIST plan on releasing the information they used to build the computer model that is still classified? Could it be you couldn't make it collapse without the explosive devices that cops, firemen and civilian witnesses kept talking about?

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