As work crews continue to clear away the rubble of the World Trade Center and the Pentagon, forensic pathologists are beginning the second round of the national effort--identifying the remains of the victims.
Because of the sheer number of victims and items to be tested, identification is a daunting task. Dr. John Butts, North Carolina's chief medical examiner, said there are several ways that forensic pathologists can identify victims.
"For most mass disasters, victims are identified by their dental work," Butts said. "This can be done through a comparison of X-rays taken of the victims prior to the attack."
Dr. Randy Hanzlick, president of the National Association of Medical Examiners, told CNN that X-rays of other body parts can also be helpful because they may have evidence of previous surgeries.
In the event that officials cannot find dental remains--a case that is likely, given the collapse of the buildings and the heat from the fires--they may use DNA comparison analysis.
"DNA analysis requires a sample from the body of the victim, and a standard sample from a blood relative of the deceased," said Dr. Tom Sporn, assistant professor of pathology at Duke. Doctors usually take that blood sample from a parent or child of the victim because they provide the closest matches.
"DNA from the victim can be extracted from many locations, such as blood, skeletal muscle, organs with high cellularity--like the liver--and bones, through molecular techniques," Sporn said.
Butts added that although blood tests are the easiest way to obtain family members' DNA, doctors often use a swab of the cheek.
"Once the sample is retrieved, it is assigned a probability, which is predicated on the integrity of the specimen," Sporn said. This probability shows the chances that the DNA of the victim does not match his relative's.
In the instance that doctors cannot perform a DNA comparison with a relative, they may retrieve DNA samples from the victim's home. "You can find DNA in items such as a toothbrush, hair brush or hat," Butts said.
Sporn added that even items that have already dried may include a viable DNA sample.
Electronic searches of fingerprints are another means by which the victims may be identified. This test has one impediment--the victim must have his prints on record.
Failing any of these methods, medical examiners can use presumptive identification, which involve items like distinctive tattoos and jewelry. Though less accurate, Sporn says it is a common method he has used in his own work.
With thousands of victims, officials hope the lengthy task of identification will be successful.
"Testing success will hold its integrity regardless of the number of bodies," Sporn said.
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