THURSDAY, Sept. 11, 2003 (HealthDayNews) -- Twice a month, on a Wednesday, the families of people still missing from the World Trade Center terrorist attacks are invited on a very painful tour.
It takes place at the New York City medical examiner's lab in midtown Manhattan, where a group of technicians still work at the laborious, painstaking process of identifying tiny shards of human remains.
This is what the families come to see.
"Every other Wednesday is a tough day," Lydia M. DeCastro, a criminologist with the medical examiner's office, says. "We cry. They cry. It's just as real for them as it is for us two years later."
Often, the loved ones have no idea how small the pieces are until a member of the staff holds up a test tube. "They still don't realize we're working with pieces, fragments," DeCastro says. "They're visualizing big pieces. We hold up a test tube. We have to explain to them. Then we cry and hug."
Of the 2,792 people listed as missing after the towers collapsed on Sept. 11, 2001, 1,524 have been identified. The medical examiner's office has collected 20,000 body pieces and has given identities to 7,857 of them.
The process, though ongoing, has slowed considerably in recent months, and Robert Shaler, chief of forensic biology for the medical examiner's office, has said that as many as 1,000 people may never be identified. There are plans to preserve the unidentified pieces at a memorial site, but the technicians have taken a piece from each piece so they can continue with their analysis.
The problem lies in the devastating and singular nature of the attack. The process of identifying victims can be likened to that of putting together a shattered vase. You start with the largest pieces and work your way down to the smallest pieces. The technicians long ago identified the large pieces and are now working with impossibly tiny fragments which, in many cases, do not yield intact genetic information.
"The big pieces have given us all the information they're going to give us," DeCastro says. "We're trying to put the puzzle back together."
A few individuals were identified with standard techniques such as viewing the remains, fingerprints and dental X-rays. Technicians then moved on to the DNA techniques which have become standard practice for solving rapes and murders, namely short tandem repeats (STRs) and mitochondrial DNA. STRs are short sequences of DNA that are repeated several times. Differences in the number of repeats can signal differences between individuals. Mitochondria are the energy centers of cells and have their own DNA which is inherited only from the mother.
Conditions at Ground Zero, unfortunately, were working against the success of these methods. Heat (fire), moisture (firefighting), bacteria, mold, exposure to fluctuating temperature and time all work to destroy DNA. "The fire burned for about three months," Noelle J. Umback, a forensic DNA analyst in the medical examiner's department of forensic biology, told the American Chemical Society's members at its national meeting this week. "The DNA has been degraded."
The final weapon in the arsenal was unsheathed this summer: a new technology which makes identifications based on single nucleotide polymorphisms or SNPs. These are single places on the DNA strand. Most SNPs will be identical from one person to another but, occasionally, differences surfaces that can help make an identification.
"These allow us to analyze the most degraded samples," DeCastro explains. "We certainly cannot use them alone. If we have a partial profile with STR and mitochondrial DNA, we can pool the results and if they meet a certain statistical threshold, we can make the identification." So far this summer, two people have been identified with the combination method and their families have been notified.
In the two years that have passed since Sept. 11, 2001, most of the medical examiner's lab has gone back to its everyday work of rapes and homicides.
Most, but not all. The identification struggle continues in one section of the lab. And every other Wednesday, the families come to view the work.
Each time, the conversation with them progresses from the vague ("specimen," "tissue sample") to the specific ("bones," "muscle") as staff members struggle to explain the process. "Our job is to interact with lawyers and detectives, not families," DeCastro says. "Now we're talking to all of the families of these homicide victims."
The families had a choice of how they wanted to be notified: each time a fragment was identified or when the whole project was done. But "done" has turned out to be an elusive concept.
"'Done' is ephemeral. We don't know what 'done' means," DeCastro says. "Every week we have a couple of new identifications, a new person. As long as we're having these sort of milestones, we can't stop."
More information
For more on DNA collection, visit the official New York City site. For more on missing victims, visit the World Trade Center Locator.
