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November 18, 1994 - Image 3

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Publication:
The Michigan Daily, 1994-11-18

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The Michigan Daly - Fr, No

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By FRANK C. LEE
Daily Staff Reporter

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DNA Double Helix
This is a model of the DNA
Deoxyribonucleic acid) structure.
NA uses four basic proteins to
record each person's unique
genetic code. This code can be
used to identify individuals in
criminal investigations.

he highly publicized O.J.
Simpson double-murder trial
is the most closely watched
courtroom event in American history,
garnering hundreds of hours of TV
coverage and reams of newsprint.
Whether Simpson is found guilty
or innocent will largely be decided by
circumstantial evidence. Central to
the prosecution's case are blood
samples found at the crime scene and in
the defendant's vehicle.
The blood samples contain DNA,
which may play an important role in
identifying the perpetrator of the brutal
murders of Simpson's ex-wife, Nicole
Brown Simpson, and her male friend,
Ronald Goldman.
If blood samples collected at the
crime scene match samples collected
from Simpson, it will cast a shadow of
guilt on the defendant that the ex-foot-
ball superstar may not be able to shed.
But Simpson's lawyers are preparing to
challenge any results from DNA testing
as being inconclusive and misleading.
Closer to home, DNA analysis is
playing a pivotal role in a series of
rapes in Ann Arbor believed to be
committed by one man since February
1992. The suspect has allegedly at-
tacked 12 women - brutally raping
five and killing one of his victims. Ann
Arbor police suspect the man is in-
volved in seven attempted rapes.
The attacks took place on the city's
west side with the latest assault occur-
ring ofa41-year-old Ann Arbor woman
as she was walking home near Com-
munity High School on Oct. 13.
The task force investigating the
serial rapist, has released a physical
description and a description the clothes
the suspect was last seen wearing. Po-
lice are now trying to connect the Oct.
13 rape with the previous cases through
DNA testing of bodily fluids left on the
woman. The tests are being conducted
at the Michigan State Police Crime
Laboratory in Northville.
DNA evidence has already indi-
cated that four of the rapes were com-
mitted by the same man, Semen, blood,
skin cells or hair are often left behind in
cases of violent crimes and sexual as-
saults. When a match is made with
samples taken from a suspect, the re-
suIts can be highly incriminating, plac-
ing the suspect at the scene of the crime.
This is what is known in criminal inves-
tigations as "DNA fingerprinting."
DNA is often thought of as the
"blueprint" for life. Short for deoxyri-
bonucleic acid, DNA is the basic ge-
netic material of life. The nucleus of
every living cell has chromosomes that
contain a string of material called DNA.
DNA controls the production of pro-
teins and carries genetic information
from one generation ofcells to the next.
All the information necessary for the
blueprint of an individual is carried
within the cell.
There are four chemical bases
strung like beads in DNA. The actual
order of these in the DNA's double-
helix structure -in which two nucleic
acid strands are wound around each
other. Except in cases of identical
twins, where a fertilized egg is split

into two genetically identical eggs,
DNA is what makes one person dif-
ferent from another.
A human being has approximately
three billion of these beads divided
among 23 different chromosomes
pairs - one from the mother and the
other from the father.
Another basic principle important
to DNA analysis is that genes that are
part of the chromosomes are inherited
randomly. It's the mixing and match-
ing of the genetic contribution from
one's parents that makes a person
unique - a DNA fingerprint.
It was only as recent as 1944 that
pioneering experiments in DNA fin-
gerprinting were done, which demon-
strated that DNA was indeed the ge-
netic material responsible for traits. Until
that time, the exact biological material
carrying the information that caused
traits to be inherited was unknown.
"Southern blotting" -- the basic
technique for DNA fingerprinting -
was first developed in 1975 and named
after its discoverer, E.M. Southern.
The first step in the technique is to
"chop" the DNA into little pieces
with restrictive enzymes from bacte-
ria. This enzyme cuts the DNA at spe-
cific sites into comparable sections.
These fragments are separated by size
over a gel film. When the gel is placed
in an electric field, it spreads out the
DNA into a smear that can be better
analyzed. The smaller pieces spread
faster along the gel than the larger
snippets of DNA.
Most of the differences between
one person's DNA and another's have
very little consequences in everyday
life - except for the analysis that
Southern blotting allows for compari-
sons between two or more living
things. On average, there are about 30
million differences between human
beings. Eye color, for example, is an
easily detectable gene that can be
traced along family lines.
A piece of paper is placed on top
of the gel to "blot' it. The DNA is
transferred to the paper. The piece of
paper then has the identical smear as
the gel. The image is then transferred
onto film, where the genes' bands can
more readily be identified and com-
pared. If a VNA sample taken from the
crime scene matches a suspect's sample
and not one taken from the victim, the
suspect is believed to have left the
genetic evidence at the crime scene.
Internal medicine and human ge-
netics professor Dr. David Ginsberg,
recently spoke at a meeting of the
University's Research Club about
what DNA fingerprinting is, how it is
used in forensic science and how ac-
curate it is.
"In one really fairly spectacular
case. there was a rape and murder in a
small town in England,"'Ginsberg said.
"They actually tested all the men in
this community and finally caught the
guy by identifying one of the men. So
it's theoretically possible to do that but
it's not something we would have an
easy time doing in this country."
Because DNA fingerprinting is
very persuasive in courtrooms, critics
claim innocent people can be convicted
if the laboratories conducting the tests
make a mistake. Ginsberg says, how-
ever, that mistakes would only exoner-
ate a person accused of a crime.
"This is also a little publicized but I
think an incredibly important applica-
tion of DNA fingerprinting - 30
percent of the time when these samples

are sent to a forensic lab, the suspect
is exonerated," Ginsberg said. "You
never hear about those cases. There's
no complaints and the prosecution
wouldn't bother trying the case.
They're innocent. There's no way it
can be them. They're off the hook."
Ginsberg has so much faith in the
accuracy and reliability of DNA finger-
printing that he "would bet my life on it."
"If I were falsely accused of a
crime, the first thing I want is DNA
testing," Ginsberg said. "That's the
easiest way to settle the issue.
But Ginsberg emphasized that DNA
testing alone is not enough to convict.

AP PHOTO
A Los Angeles police criminologist examines O.J. Simpson's Ford Bronco two months after it was seized in this
photo taken in late August, to be published in the December issue of LIFE magazine. Evidence reLted t
Simpson's vehicle - including blood samples - has been the subject of court proceedings,.

In sexual assault cases, chances
are that genetic material is often left
behind by the perpetrator.
"In rape cases, it's been particu-
larly effective tool because rapists
generally tend to leave behind a
sample of their own DNA," Ginsberg
said. "Semen is basically just a bag of'
DNA. It's a very good source of DNA.
It s ery easy to separate f rom the rest
of the material of the victim."
DNA samples of that sort are diffi-
cult to leave behind in an innocuous
way. "When the semen sample is
there, it's a little bit harder to explain,"
Ginsberg said. "'It just fell off when I
was passing by,' is a little harder to get
away with, harder to explain."
Genetic testing is done by various
forensic labs around the country and
the FBI. Many of the initial problems
with DNA testing stemmed from its
early development. Ginsberg now feels
that any errors are not the result of the
actual test when it is done properly,
but rather errors committed by a hu-
man factor such as the technician con-
ducting the tests or the way the police
gathered the evidence.
"Is DNA testing foolproof "
Ginsberg asked. "DNA testing is not
foolproof. One of the potential prob-
lems is that they may be right about
the identification but still have the
wrong guy. Samples could be mixed
up. Someone could be framed. All
sorts of things could be going on and
that has to be kept in mind."
DNA evidence, Ginsberg reiterated,
cannot stand alone as the only indicator
of guilt. Other evidence presented by
the prosecution must come into play.
"All you can say as an expert is
whether or not DNA came from a
particular person," Ginsberg said.
"Other than that, you really can't say
much and the rest a jury has to decide."
Ginsberg dismisses complaints as
to the accuracy of DNA testing as
legal maneuvering rather than sub-
stantive claims. "All expert scientists
agree that DNA is the genetic mate-
rial, that DNA differences can be
tested by Southern blotting," Ginsberg
said. "You'll find absolutely no argu-
ment among any reasonable, credible
scientists. But there is argument, there
has been controversy..."
The sideshow bantering between
expert witnesses brought in by the
prosecution and defense is what has
led to the confusion in the public's
mind but there is no confusion in
Ginsberg's mind.
"In my mind, they're missing the
forest for the trees," Ginsberg said.
"This is very, very good evidence.
It's better than anything they've had
in a court of law before. But when you
get one expert testifying, 'Well the
odds of this being someone else is one

probably for a hundred years. ... The
major difference is that they've never
been asked to do that. The evidence was
accepted long ago and never debated."
Even if DNA testing is not as
foolproof as its critics claim, it is stil
one of the most accurate kinds of
evidence in existence. "DNA testine
at its worst is as good as five or six
eyewitnesses saying, 'That's the
guy, Ginsberg said.
There are still some improvements
to be made in DNA fingerprinting, but
for the most part, it has been admissible
as evidence in a court of law.
"There are still lots of issues,"
Ginsberg said. "It's not standardized.
The testing labs are not regulated. All
of these are going to be ironed out and
they should be."
"It has been uniformly accepted in
Michigan and it's not even fought here
much anymore," he said of DNA evi-
dence being contested. "It still is a little
bit in California as you well know."
It doesn't take a huge amount of
genetic material to conduct these tests,
contrary to what one might expect.
"To do a standard Southern blot,
you need somewhere between a few
hundred thousand cells to a million or
so cells," Ginsberg said. "That sounds
like a lot, but a single drop of blood has
enough to do that kind of analysis."
Another remarkable aspect of
DNA is its durability under adverse
conditions. "DNA is pretty stable stuff
under the right circumstances but it
can break down," Ginsberg said. "Ex-
posed to the environment, just sitting
outside on a bloody glove lying on the
ground for example, it's stable for
weeks and months."

Even when it breaks dowtn, it vwould
not have any negative imphcation
"It woni tchineone bind of DNA
to another and that's the cri ..ical thin ,
cesberesaid.'ii " t makevoilook
like me just h\ sitin awround . 'You
don't get false positiveCs. You get htlse
negauives.
ince k NA eidence la-s sch a
crucial role in criminal in',esigations,
it ofien becomes a targ~e1 I or criticism.
Ginsberg believ.es that IDNA testing
shotild be the least of the court's con-
cerns. ''There's this savinie about the
chain being as sTr'a. as its weakest
link,' Ginshere sad "You got all
these links the policeman at the
crime scene gathering the blood, the
technician in the lab. Right there in
the middle ithehe DNA testing - the
biggest, fattest link. Some people are
worrying how strIong that is vhen
there are other things more likely to
be a source of eri'or than the DNA
testing itself.
Ginsberg pIredicts other uses for
DNA fingerprinting are on the hori-
zon but there are also ethical implica-
tions to consider as well.
"The army had a big prog'am once
to DNA fingerprint ewerybody who
went into the army - thinking that,
you know, it would be tremendously
useful for them," Ginsberg said. "If
somebody was blown up and all you
got was a little bit of their shoe with
blood in it and you want to find out
who that was, xou could now identify
them. There would be a lot less miss
ing in action. 01' course it raises the
specter of everybody's fingerprints
of being in this database and Big
Brother.'

Chemical base pairs of DNA

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