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Features May 2004: Volume 1, Number 2

One in a Trillion
On the Job: David Fisher, '97
Raymond Hardie


David Fisher is a criminalist. It's a term Fisher delivers with an engagingly lopsided smile, as he savors its almost Victorian quaintness. Then he adds, "not to be confused with a criminologist, who works on the social science aspect of criminal justice." Specifically, he is a forensic scientist in the forensic biology laboratory at the Office of the Chief Medical Examiner in New York City. I joined him one morning this summer as he took the service road from the offices and labs on First Avenue to Bellevue Hospital three blocks south. It is hot and humid, the road is dusty and traffic rumbles by on the FDR expressway overhead. But Fisher walks at a clip, keen to show the new mitochondrial (mt)DNA labs on the 9th floor of Bellevue.

As we walk, we see a large white tent behind a cheap wire fence. A wood-paneled double door, framed in the middle of the tent's front wall, is securely locked to maintain privacy. And as we glance along the inside of the fence, faded photos, drawings and plastic flowers stir in the breeze from the East River. It is a place that demands you stop and look.

Now a memorial chapel for the families of the 9/11 victims, the tent is divided into two with the front section holding the chapel. The back section has a number of walk-in freezers that contain the remains of those victims who have not yet been identified and they will stay stored in these freezers at "Memorial Park" until a permanent memorial is built at ground zero. Of the 2,749 who died, 1,562 have been identified and those remains were returned to the families. The work on the 1,187 unidentified remains will be suspended in September until more sensitive DNA technologies can be developed. When the World Trade Center collapsed, each burning tower acted like a mortar and pestle grinding and twisting as it fell, so that the victims were virtually obliterated. "Because the remains were so commingled, we did not know if we had one person or two people or three in the mix of bone and tissue," Fisher says. Finally the fire was doused with large amounts of water and the site was exposed to the elements for months before it was cleaned up. The result was that some of the nuclear DNA became badly degraded.

" I was an intern here when 9/11 happened and I got hired afterwards," Fisher says. "We were working 24 hours a day. It was slow going, but finally we were able to generate some DNA profiles from these remains. The lab had no idea if they were going to be able to handle the volume of work. But the decision was made that we would go ahead and try to process all the remains, try to identify them. After all, it was the largest crime scene, ever, in history." A crime scene. While the much-played video of the falling towers has burned itself into our national psyche, the scientists in the medical examiner's office continue to work on the crime scene, slowly, methodically, one piece of evidence at a time.
We stand for a moment looking at the wall of remembrances, a child's drawing of his father, a Xeroxed photo, fragments of poems, and then start along the service road to Bellevue. "They had counselors available to us after 9/11, and they were somewhat helpful," Fisher says. "Really it was good to go, because it was a group session, people talking about their experiences."

The forensic biology lab is organized on a rotation system. Each person works in one of the areas for a week and then moves on. This means that the criminalist who examines an item of evidence is usually assigned that case. There are about five criminalists on evidence examination at any given time but, with the volume of work, an analyst can expect to receive a couple of cases a day. Although many other specialists will work on the evidence as it is processed through the system, that first person will write the final report and testify on the results if the case goes to trial.
During his two and a half years on the job, Fisher has opened many evidence packages in Bellevue's processing rooms. On average, the lab receives five to ten evidence packages each day. As we walk inside, the temperature plunges, and the chaos of ambulances, overcrowded waiting rooms and noisy corridors gives way to a studied clinical quietness. Two specialists examine a pair of black running pants, carefully laid out on a sheet of brown paper. One of them outlines the pants in pen, and measures the length and angle of the zigzagging knife cuts. Then she circles bloodstains. Small portions of the stained material are cut out, swabs are taken, and everything is secured in plastic Eppendorf tubes for DNA extraction. Meanwhile the other specialist takes digital photos, makes sketches and writes out the notes. Everything is noted. Each case has an evidence unit tracking number. It is also assigned a forensic biology number, in order to assure that a clear chain of custody can be established all the way through to the trial phase.

As we walk out, leaving the specialists to their slow and methodical work, Fisher says quietly, "I once had a rape victim say thank you to me when I testified. You get a great deal of satisfaction from that."

But how do Fisher and his colleagues deal with exposure to those kinds of crimes on a day-to-day basis? "I've learned to compartmentalize things. Not to take work home with me, although I occasionally talk about certain cases with my wife," he says. "The thing that really gets to me is when children are involved. I have a 14-month-old son and I had a difficult case with a young child involved. Those cases can get to you."

The DNA labs are in the medical examiner's offices. The evidence samples are taken there and the DNA extracted. In rape cases the lab performs what is known as a differential extraction since it is most likely that male DNA from the perpetrator and female DNA from the victim are mixed together. The fact that the sperm cells and epithelial cells have a different morphology allows them to be separated. After the extraction step, the lab generates thousands of replicas of the DNA using a procedure called the polymerase chain reaction (PCR).

After PCR, a process called electrophoresis (during which fragments of DNA are separated by size) generates fluorescent data that is analyzed by a computer. The DNA specialists are interested in 13 locations or loci, which together generate a DNA fingerprint, or profile.

This profile is unique. The possibility of any two people (unless they are identical twins) having the same DNA is one in a trillion. "It's hard for the public to think about what one in a trillion means," Fisher says. "But essentially if you were to sample the population at random, the chance of somebody else having your DNA is impossible."

The DNA profile obtained from the evidence is the basis of a report that is uploaded into CODIS, the Combined DNA Indexing System, run by the FBI. In CODIS, the13-loci profile is compared with other cases or convicted offenders. But there may be no match within the system and since there is a statute of limitations for certain crimes (for example rape cases in New York State cannot be prosecuted after 10 years), criminalists often find themselves in court testifying against a John Doe with a specific DNA profile. Thus the crime is solved even though the perpetrator is yet to be found.

Fisher has of course testified in a number of cases. "One of David's greatest assets is being cool under pressure. This trait is extremely valuable when you need to defend the DNA results in a court of law," says Paul Goncharoff, Ph.D., who is setting up a new mtDNA lab with Fisher and Jason Kolowski, another analyst, this fall. "David also has excellent communication and teaching skills, which contribute to making him an excellent witness."

At UCSD, Fisher majored in biochemistry and cell biology, but it was an undergraduate internship at the Salk Institute that stimulated his ongoing fascination with DNA. "That was the first research lab I worked at and I was fortunate to meet the late Francis Crick, the father of DNA," Fisher says. "I still remember his license plate ATGC, which is the DNA base pairs (adenine, thymine, guanine, cytosine)." Originally in pre-med, Fisher began to consider a career in the relatively new field of forensic biology. He started his graduate work in the forensic science program at John Jay College of Criminal Justice in New York in 1999 and was hired at the medical examiner's office a few months after 9/11.

The first U.S. conviction based on DNA evidence was in a Florida rape case in 1987. New York City started processing DNA cases in 1996 and the department has been aggressively expanding ever since in an attempt to keep pace with the constantly evolving nature of the science. One measure of the burgeoning success of forensic biology is the CSI-type dramas on network television. The one-hour quick-solution plot lines, the blinking lights and the music may be missing from the no-nonsense labs on First Avenue but the underlying message is the same. Science does solve crimes. And each year that science becomes more complex.
Witness to this is the new mtDNA lab located on the 9th floor of Bellevue. Fisher is one of a team of three, led by Goncharoff, who will launch this new facility, one of only a handful in the country that will do mtDNA casework. "We'll hopefully be able to get mtDNA results from cases, where there is an insufficient amount or quality of nuclear DNA," says Fisher, pointing out the rows of new machines and the glistening antiseptic benches with obvious anticipation.
MtDNA, which is found in bones, teeth and hair, is less susceptible to degradation than nuclear DNA. This is because it is smaller and exists in a circular genome, which offers protection, unlike the double helical structure of nuclear DNA. For example, the DNA inside a tooth will be well preserved behind the enamel, and mtDNA can be obtained by grinding the tooth or cutting off the crown and taking out what's inside. Also, the copy number to the mtDNA molecule can be as high as 100,000 per cell, whereas the copy number for nuclear DNA is two (one from the mother and one from the father). "So the chances of getting a profile from mtDNA are that much greater than with one nuclear DNA," says Fisher.

" MtDNA is especially useful in missing person cases where investigators may not have a reference sample for comparison to the evidence recovered from the crime scene," says Goncharoff. "This is not a problem with mtDNA, since any maternal relative of the missing person can have their mtDNA type determined and used as the reference sample."

It was such a matrilineal detective case that first caused Fisher to become interested in mtDNA in graduate school. In 1991, the presumed remains of Czar Nicholas II and his family were exhumed in Yekaterinburg, Siberia. The gravesite was not far from where the Czar and his family were murdered in 1917, and nine bone samples found at the site were subjected to mtDNA testing. Since mtDNA is maternally inherited, it means that a mother will have the same type as her children. But a male will not have the same type as his children. A sample that was presumed to come from the Czarina Alexandra was tested against a sample provided by the Duke of Edinburgh, who is her grand nephew. It matched, thus proving the bones were indeed those of the Czarina.

As Fisher prepares to start work in the new mtDNA lab with his colleagues, he anticipates solving mysteries of all kinds. From murders that happened yesterday, to decades old crimes, to the occasional historical puzzler and scientific teaser. "This field combines all of those interests," Fisher says. "I enjoy the work. Every day is different. It is a constantly changing field and I hope to stay with it." Then he adds with a smile, "Plus, I always liked murder mysteries and police work."

As we walk out, a young policeman is delivering a yellow envelope. The white tape sealing it reads "evidence" in bold black letters. I learn later it is a rape kit.
" You can't help but have a deep sense of satisfaction when your work helps put some bad guy behind bars," says Fisher, "or helps release someone who's innocent and has already been wrongly imprisoned."

Raymond Hardie is the UCSD Alumni Association editor. He lives in Del Mar.


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"It's hard for the public to think about what one in a trillion means... but essentially, the chance of somebody else having your DNA is impossible."