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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