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Forensic
DNA
 Over
100 years ago fingerprinting because the most accurate
way to place a suspect at the scene of the crime. The
technique was revolutionary and put many criminals behind
bars. Now, however, a newer and more accurate method is
being used: DNA testing, and it’s just as revolutionary,
if not more so.
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Although
DNA testing takes time--usually several weeks because
of the legwork involved in matching base pair sequences--it
is highly accurate; in one case, the odds that the
match was incorrect were 350 million to 1! This
makes DNA tests the most accurate piece of scientific
evidence a lawyer can have.
The
process is simple: two samples are taken, one from
the suspect and one from the scene of the crime.
The samples can be skin tissue, hair, blood, semen
or vaginal fluid, and really anything else with
cells in it (the two samples don’t even have to
be the same material because all cells of the same
organism have identical DNA). Then, the DNA of both
samples is extracted, studied, and compared. If
the DNA matches, then the suspect was at the scene
of the crime.
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DNA test results
By
permission University of Illinois
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The
techniques was first used in the late 1980’s to convict
a Portland, Oregon, man of raping and impregnating his
13 year old daughter. Tissue samples were taken from both
the man and the fetus (which had been previously aborted)
and the DNA was analyzed. The results were conclusive
and the man confessed. The test was remarkable not only
in that it provided concrete evidence, but also because
the samples compared weren’t from the same organism (the
fetus had both the man’s and girl’s DNA, yet scientists
were still able to find common sequences).
Since
the late ‘80’s, DNA has been widely used in the courtroom.
It was used as evidence in the 1995 O.J. Simpson trial.
It was also used to clear deceased Sam Sheppard, the famous
physician who was accused of killing his wife in 1954,
but claimed a “bushy-haired” man did it (this true story
inspired the TV series and movie “The Fugitive”). A DNA
test proved that the blood at the murder scene wasn’t
Sheppard’s or his wife’s--meaning someone else was there!
This story is similar to countless others: since the advent
of DNA testing, dozens of wrongly-convicted men have been
pardoned and released.
Even
DNA from animals has been used. In one case, a murder
suspect accused of killing a couple and their dog was
convicted after a DNA test proved that the suspect’s jacket
had the dog’s blood on it. And in California, a poacher
was sentenced after a DNA test proved that his refrigerator
contained venison from eight different deer (six more
than the legal limit).
DNA
testing is the most accurate form of scientific evidence
available--within millionths of a percent! It’s allowed
the justice system to easily find the criminals--the right
criminals--and keep them from harming society.
    
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