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Truth Over Death 

A Berkeley forensic mathematician, the herculean effort to identify World Trade Center victims with DNA, and the value of closure

Wednesday, Mar 6 2002
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In New York, 18 refrigerated trailers contain one of the more bizarre mathematical problems ever contrived. The human remains within the trailers -- some 14,000 bits of decomposed, charred flesh and bone, most of it so degraded that only the bone marrow is useful for scientific analysis -- await scientists, who turn each fragment into numerical representations of genetic code. To complete the puzzle of matching faceless remains to names, officials in the New York Medical Examiner's Office have undertaken a massive effort to gather hair strands, toothbrushes, used Chap Stick, and other sources of genetic material from the homes of hundreds of World Trade Center disaster victims. In cases where this isn't enough to produce a genetic match, officials ask surviving relatives for samples of their own DNA.

New York is pursuing a missing-persons investigation greater than any ever undertaken, attempting to match random body parts from the WTC disaster to more than 2,800 victims' names. At the heart of this quest, a Berkeley mathematician writes, and rewrites, software designed to sift through mountains of genetic code. This most macabre of mysteries -- to whom did these thousands of tiny, faceless pieces belong -- is also fantastically complex. Given the intricacy of every bit of genetic code, it's something akin to finding patterns among the stars in the cosmos, then matching them, precisely, to patterns among grains of sand.

By some measures, the World Trade Center DNA project is also a gargantuan exercise in futility: Of approximately 900 DNA profiles with a potential to be matched, Berkeley forensic mathematician Charles Brenner says investigators have so far matched only a quarter of these remains using DNA analysis. Some 1,800 victim families have requested death certificates based on non-DNA evidence showing that their relatives were in the buildings at the time of the disaster.

Despite its limited success, this mass genetic-matching effort is actually far from pointless. Following massacres in Africa, South America, and Eastern Europe, where international experts spent years exhuming murder victims to help families learn what had happened to loved ones, human rights experts now believe that there's nothing like truth to help people recover from atrocity.

If the World Trade Center DNA project has an elegant goal, its execution -- digging through piles of rubble to find body parts, then knocking on doors to ask for DNA-laden mementos to use in the matching process -- has been a particularly inelegant exercise for Brenner and his colleagues.

Still, it's the kind of monumental mess of the sort Brenner has spent more than a decade preparing for. Perhaps the world's only freelance forensic mathematician and one of the planet's foremost experts in solving the numerical equations required to match DNA samples, Brenner has traveled to Argentina, where he wrote software that helped establish the parentage of some 300 infants given to childless military families after their biological parents were murdered by agents of that country's 1970s-era military dictatorship. Brenner wrote algorithms that helped swiftly identify all 229 victims of Swissair Flight 111, which crashed off Nova Scotia in 1998. And Brenner's mathematical tools helped resolve paternity questions related to Larry Hillblom, the Bay Area multimillionaire and DHL delivery service founder who sired at least a half-dozen heirs in liaisons with teenage girls in Micronesia and East Asia.

As with these previous cases, much of the WTC effort involves ordinary detective tasks such as digging up remains, categorizing evidence, and knocking on doors. But in New York, as elsewhere, matching genetic information winds up being above all a mathematical puzzle; the heavy lifting of DNA fingerprinting science lies in calculating the mathematical probability that seemingly random markings in one genetic fragment are biologically related to similar pieces of DNA code in another. Seeking to match thousands of body parts with thousands more DNA samples and/or family members presents a forensic number-crunching task like no other tried to date.

Given the magnitude of the job, ordinary DNA techniques fell far short. Matching 14,000 body parts with material from thousands of family members would take years to complete if standard methods were used, Brenner says. "You would be swamped by plausible relationships between nonrelatives," says Brenner.

At first it was far from clear which techniques would prove most effective in sorting information from the World Trade Center remains. Investigators convened a forensic science summit of DNA experts from around the world. Experts considered software used by the FBI, but it turned out the FBI software was of little use matching massive amounts of DNA information from relatives.

"Starting with the first meeting, I started agitating to get the data," says Brenner, who flies again this week to Albany for a meeting of the committee formed to advise the World Trade Center DNA project. "Not knowing any more dignified way to put it, I spoke up at the meeting and said, "Give me the data, and I'll solve the problem.'"

New York officials relented, and Brenner went to work, eventually writing a DNA-specific version of today's intelligent Internet search engines. "If you're a little more clever, and let's say you have two family members in a given reference family, two living references, and you make sure both of them appear to be related to a given victim before the computer gives any signal, then you filter out the majority of the false matches," he says.

"After I had the data, it only took me a week or so to extract the available information from it, which I passed back to New York," he adds. "And they gave me some more sample data."


Looking past Dr. Brenner's excitement at the intellectual challenge presented by the World Trade Center DNA project, it's possible to question the wisdom of spending thousands of man-hours on a forensic effort doomed to achieve only modest investigative success. Last month New York officials asked family members to scour their homes for more DNA-marked remnants of loved ones -- dirty clothes, hairbrushes, anything. But even this second call for genetic material is unlikely to produce a thorough catalog of the World Trade Center dead. Too many people were made cinders by the heat of the jet fuel explosions involved; the cataloging of remains has lacked the kind of precision that might have been possible were this a smaller crime scene; in many cases, producing sufficient genetic material from victims' families won't be practical. Out of fewer than 900 fragments with DNA profiles that provide the potential to be matched with those of family members, the New York Medical Examiner's Office has so far only produced a couple of hundred actual matches as a result of DNA, Brenner says.

If a WTC banker happened to be outside sipping coffee Sept. 11, saw the explosion, then decided to abandon his family and start a new life in Malibu, the massive forensic effort under way in New York would have absolutely no chance of foiling the scheme. From a police-work point of view, the identification process is nearly pointless.

But a volunteer team of 1,000 scientists, forensic experts, and funeral specialists continues to perform this unimaginable task. Workers from mortuary teams wade through the rubble, filling buckets with any trace of survivors. DNA specialists analyze the buckets' contents and convert the results into endless rows of numbers, which are crunched through successive versions of Brenner's software, which he continues revising as new data comes in. Given the meager results, Brenner says, "digging through this is a little disappointing in a way."

But the dig continues, and for good reason.


Though America's public discussion of moral issues surrounding recent advances in genetic technology has focused on stem-cell research and cloning, the discussion's most fascinating ethical terrain, in my view, involves the interplay between DNA and human rights. It just so happens that the era of greatest advancement in genetic typing technology has coincided with an epoch of global atrocities.

Groups such as Physicians for Human Rights have fought for the right to use DNA technology so the families of victims in Africa, Central and South America, and Bosnia can know what really happened to their loved ones. Now, more than a decade after DNA was first used to prove the identities of the Argentine desaparecido orphans, the international community places a high value on the curative power of truth.

Argentine scientists, who gained expertise working on efforts to learn the truth about people who disappeared under that country's military dictatorship, have gone on to Zimbabwe to help communities learn the truth about massacre victims there. Bosnian experts have aided in gathering information about the World Trade Center tragedy. They've seen families stand waiting at the edge of mass grave sites as forensic experts sift the remains, and the experts now understand the strength of the desire for knowledge.

"When there's been an atrocity, people search for information to guide their future. They search for information on how the event occurred, and why it occurred," says UC Berkeley visiting scholar Laurie Vollen, who directed the efforts by Physicians for Human Rights to identify human remains in Bosnia. "Atrocity takes you out of your concept of the world, so you try to break it into pieces you can understand. These questions are the quest for truth, and they are insatiable."


It's for this reason that DNA identification efforts such as Brenner's may just be worthwhile. It's also for this reason that I've so far devoted four columns, and am now devoting part of another, to the San Francisco Police Department's practice of choosing secrecy over transparency when it comes to public access to official records on deaths in which police officers have been involved. In the case of the World Trade Center, workers and scientists are moving heaven and earth to give families some certainty about the nature of their loved ones' deaths. In San Francisco the official posture regarding police-involved death is exactly the opposite.

In the case of Gregory Caldwell, the Mervyn's shoplifter who asphyxiated in police custody in December, and Idriss Stelley, the computer student police shot to death in the Metreon movie theater last summer, police withheld official information for months, refusing to release police reports and medical examiner's reports until the story of the deaths was, in journalistic terms, dead. Our Police Department uses a little-noticed clause in state public records law, which says that official documents may be withheld in cases where their release might obstruct an investigation, as a blanket cover for concealing documents pertaining to police-involved deaths.

As a result, in both the Stelley and Caldwell cases, family members anguished, wondering why their loved ones had died. In both cases, documents containing the answers were kept secret for months -- and the anguish of survivors was prolonged.

Last week I finally obtained the medical examiner's report on Caldwell, the shoplifting suspect who died Dec. 3 in police custody after complaining he couldn't breathe. As I described in a previous column, police held Caldwell in a "hobble" device, a controversial leg restraint, the misuse of which has been blamed in suffocation deaths around the country.

For two months police would not say exactly how the hobble device had been employed in this case, even though -- or perhaps because -- this information was crucial to determining whether department policy allowing use of the device had led to Caldwell's death. Family members and the rest of the public were left to speculate as to how Caldwell really died. His mother, as I reported earlier, had nightmares that he had been lynched.

As it turns out, Caldwell died of "restrictive asphyxiation," according to the medical examiner's report; that is to say, it does appear that the method police used to restrain him caused him to suffocate. But in the final analysis, S.F. Medical Examiner Boyd Stephens says, use of the hobble device didn't kill Caldwell. Police didn't hogtie Caldwell, as has been the case in suffocation deaths in other cities where the hobble device was misused. Rather, Caldwell died because he was left on his stomach, gasping for air with his hands handcuffed behind his back. The fact that Caldwell had large amounts of cocaine in his system, and that he had been engaged in an exhausting struggle with officers, made this body position particularly deadly.

"If he were sitting up, or even on his back, he may have gotten enough air. His position, in our judgment, does play a part in his death, and does play a significant part. We put the asphyxiation first, and linked it to the cocaine," says Stephens, who examined a security video of the incident. "He's face down. He's a heavy person. His breathing is restricted in the struggle."

So Caldwell's death becomes less a debate on use of a controversial restraint device, and more a question of how, precisely, police should temper their use of force. Police frequently find themselves needing to subdue powerful, violent, large criminal suspects without getting hurt themselves; handcuffing behind the back has a long, successful track record in this area. And it's nearly impossible to handcuff a violent person behind his back without throwing him on his stomach.

In the case of Gregory Caldwell, police didn't seem to realize when the fight was over. After he was fully restrained, Caldwell told officers he couldn't breathe. Apparently, police didn't believe him. One officer even told Caldwell he'd be allowed to get up if he stopped struggling.

"It's my understanding that they said, "When you stop fighting, we'll let you up.' But when a person is struggling for air, it's hard for him to stop fighting," Stephens says.

Ideally, San Francisco residents might join a public discussion of the appropriate way to educate police in the use of restraint against violent suspects, so that police don't inadvertently kill. This is the type of subtle, two-sided discussion that democracy, and its incumbent public information laws, routinely handles with aplomb.

Unfortunately, the SFPD appears wary of this process, preferring secrecy to debate. In other cities, police-restraint deaths lead to extensive press coverage, public outrage, public discussion, and police reform. In San Francisco, SF Weekly is the only paper that's reported on Caldwell's death. Police withheld public documents on the case for two months, while the department's public information department offered statements apparently intended to mislead.

The SFPD public information office appears to have perfected a good cop/bad cop routine for cases such as Gregory Caldwell's. Good cop press officers congenially offer that it's up to homicide inspectors to release information; inspectors don't return calls. Good cop press officers say the City Attorney's Office has told them to suppress documents, when the City Attorney's Office has clearly given no such instructions.

Outside San Francisco, human rights activists pour massive effort into truth commissions, atrocity investigations, and forensic studies of DNA, so that citizens might make better sense of their world, then improve it. The case of Gregory Caldwell suggests that it's high time for San Francisco's Police Department to join this effort by releasing information pertaining to officer-involved deaths in a timely and transparent fashion.

About The Author

Matt Smith

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