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Back to Archives | Back to September 2011 Contents 

Handling Mass Fatalities: Advancements since 9/11 by the Office of the Chief Medical Examiner’s World Trade Center Identification Unit

By Mark Desire, Assistant Director of Forensic Biology, New York City Office of Chief Medical Examiner

issing persons and unidentified human remains are a tremendous challenge to state and local law enforcement agencies. In 2007, a National Institute of Justice study estimated that as many as 40,000 cases of unidentified human remains were then being held or had been buried by medical examiners’ and coroners’ offices throughout the United States.1 Many crime laboratories do not have the ability to perform DNA analysis on old or degraded human remains, further exacerbating the problem of unidentified decedent caseloads. Helping the forensic community to reduce the number of cases involving unidentified remains by advancing the DNA techniques developed during the last 10 years is a driving factor behind the human identification work being done at the New York City Office of Chief Medical Examiner (NYC OCME).

The ability to tell physical characteristics from a person’s genetic material, such as identifying eye, hair, or skin color from a bone fragment or a drop of blood, was not possible until recently. This new application of DNA technology, currently being researched and performed at the NYC OCME, may provide an additional tool for investigators to help solve a crime or identify an individual from the smallest amount of remains or evidence left behind.

The World Trade Center Identification Project

On 9/11, two hijacked commercial airliners struck the Twin Towers at the World Trade Center (WTC) in New York City. The 2,752 victims of the attack on the WTC included 343 firefighters and paramedics and 60 police officers from New York City and the Port Authority of New York and New Jersey, and a member of the Secret Service.2 When the towers collapsed, victim remains became severely fragmented and difficult to identify. The NYC OCME and hundreds of law enforcement personnel, doctors, nurses, students, dentists, funeral directors, and scientists came together and began a massive identification process.

To date, a total of 21,812 pieces of human remains have been recovered from New York City’s Ground Zero and examined by the NYC OCME. The major goals of the investigation, which began in 2001 and continues to this day, are determination of cause and manner of death, the identification of decedents, the prompt issuance of death certificates, and the collection of evidence. Ten years later, there have been 1,626 (59 percent) identifications for those reported missing. The WTC Identification Unit remains committed to the process and works full time to identify those killed on 9/11. Historically, this is the United States’ largest forensic investigation, and the experience has led to major improvements in DNA techniques.

Preparing the equipment

The process begins with an anthropological review of the remains to determine which section of bone would be ideal for DNA extraction and preparation of the bone sample. The bone fragment is then cleaned and dried to remove any moisture, which can degrade the results and hinder profile generation. The bone is then weighed and measured. Additional dirt, tissue, or other material is removed from the bone with a disposable scalpel and through washing with water and an enzyme active powdered detergent solution. If the fragment is larger than 0.5 grams, a section of approximately that size is cut to ensure the best possibility of generating a DNA profile.

The next step involves milling or grinding the bone fragments. This generates bone dust, allowing access to the most cells possible and increasing the chance of identifying the individual. The bone dust is decalcified and incubated overnight to remove any remaining moisture, and the isolated DNA is quantitated to determine how much human DNA is present. Properly preparing the bone dust and extracting the most DNA possible are vital to allow the next step in the process—amplification and profile generation—to be successful.

The final step involves amplifying the existing DNA to generate enough for a profile. The polymerase chain reaction generates millions of additional copies of a particular DNA strain using primers for the 15 core DNA locations. These core locations are used for standard casework by all DNA crime laboratories throughout the United States. Once a profile is generated and analyzed, the information is entered into the WTC Combined DNA Index System database and compared with all the other bone profiles and reference samples collected during the last 10 years to determine if a match exists.

Using and Improving DNA

Incubation of samples
DNA analysis, combined with anthropologic expertise, has become the standard method for identification of victims from the WTC disaster. DNA techniques have usually been employed as a last attempt for mass fatality identification, only after quicker methods such as dental comparisons and traditional fingerprinting. In many mass fatalities, including that at the WTC, dental comparisons and fingerprinting are not possible, so DNA testing becomes the most conclusive mode of identification for fragmented remains. Through the NYC OCME’s efforts to identify severely compromised remains, DNA extraction and analysis technology has vastly improved. The process of extracting DNA has been refined to give the greatest possible yield of DNA from bone fragments. These improvements are currently being used to obtain DNA results from badly degraded and fragmented human remains of WTC victims that previously gave no DNA results.

Additional DNA technologies and software will further enhance future identification projects. Equipped with a staff of scientists who have experience from the decade-long massive identification effort, the NYC OCME is prepared to optimize and implement these new tools and disseminate this knowledge to other agencies.

The efforts of the NYC OCME have taken DNA identification to the next level by advancing missing person identification capabilities. The number of missing persons and unidentified human remains in this country is astounding. There are as many as 100,000 active missing person cases in the United States.3 Every year, thousands of people disappear under suspicious circumstances. Each missing person case is assumed to be a homicide until proven otherwise. The identification of the missing plays a vital role in how each case will be investigated.

Lessons Learned from the WTC Disaster

Mark Desire in the green shirt on New Jersey
State Police boat after South Tower
collapses on the team
Mark Desire and OCME partner Brian
Gestring evacuated to New Jersey after
South Tower collapsed

Lessons learned during the WTC identification project have led to many system improvements in death investigation. Most significant is the development of better methods for gathering antemortem data.

Postmortem data are information collected at the morgue to make comparisons; antemortem data are information such as physical description, identifying markings, medical and dental records, and DNA collected from family members of the missing. The antemortem data drive the identification process and are vital in returning remains to families.

The NYC OCME has developed a Unified Victim Identification System to allow both law enforcement and medical examiners to collect and combine antemortem and postmortem information, making identifications as quickly and efficiently as possible. This system is available for free upon request to any other jurisdiction in need.

Continuing Efforts to Bring Victims Home

The NYC OCME will continue working to identify every victim of the WTC disaster. There are several important reasons why the project is so critical.

Bringing closure to families. First and most important to the NYC OCME is the communication of information to the affected families, helping them reach closure and continue with their lives. Discovering that a loved one has died is not easy, but it is much better than not knowing what happened.

Issuing a death certificate. In New York, the medical examiner’s office is the only agency allowed to issue a death certificate. Without proper documentation, victim’s families cannot collect critical death benefits that can make a huge difference to those struggling both financially and emotionally.

Delivering justice. The third reason is related to crime scene reconstruction for the purposes of collecting evidence and information to identify potential suspects and victims. Determining cause of death from an obvious mass fatality may seem like time wasted, but opportunistic homicides, such as those observed during the Hurricane Katrina recovery, should be ruled out to facilitate identification of potential suspects and terrorists.

Memorializing the victims. DNA profiling has helped identify five of the nine terrorists on board flights that crashed into the WTC. The remains of these five terrorist have been separated from the remains of the victims. It is important to families of WTC victims that the perpetrators not be among the remains honored with the WTC memorial, which will contain all of the remains that have not been identified or claimed by the families.

As the WTC identification team works to finish this massive investigation, the lessons learned and technology developed out of necessity may be of help to law enforcement and medical examiners during subsequent mass fatality or missing person cases. The agency continues this tradition of working together for a common cause. ■

Mark Desire is assistant director of forensic biology at the New York City Office of Chief Medical Examiner. He can be reached at or (212) 323-1215. For further information on mass fatality or missing person identification, please contact Mark Desire or visit the NYC OCME website at


1 Nancy Ritter, “Missing Persons and Unidentified Remains: The Nation’s Silent Mass Disaster,” NIJ Journal, no. 256 (January 2007), (accessed June 29, 2011).
2 Henry Goldman, “New York, U.S. Commemorate Sept. 11 Anniversary with Ceremonies, Protests,” Bloomberg, September 12, 2010, (accessed June 29, 2011); and “ODMP Remembers Master Special Officer Craig J. Miller,” Officer Down Memorial Page, (accessed June 29, 2011).
3 Ritter, “Missing Persons and Unidentified Remains.”

Please cite as:

Mark Desire, "Handling Mass Fatalities: Advancements since 9/11 by the Office of the Chief Medical Examiner’s World Trade Center Identification Unit," The Police Chief 78 (September 2011): 26–28.

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From The Police Chief, vol. LXXVIII, no. 9, September 2011. Copyright held by the International Association of Chiefs of Police, 515 North Washington Street, Alexandria, VA 22314 USA.

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