A L U M N I M A G A Z I N E - Colby-Sawyer College

Kim prepares the ABI 310 genetic analyzer for a DNA run. By the time the 15 markers generally used in profiles in forensic laboratories are examined, it is not
uncommon to find a profile so rare that, when it is entered into a statistical program, the likelihood of finding a match in the general population may be represented
at one in five quintillion.
the distribution, size of spatter, and patterns of blood at a crime
scene, or on a person’s clothing, or on a weapon, or wherever
blood is found. What I’m actually doing in these situations is
evaluating the blood stains and determining what I can say
about them and what they may represent in terms of what took
place to make those patterns.
“For example let’s say I find a castoff pattern, which happens
when somebody has used a blunt object like a bat. As they
swing the bat it’s going to cause a linear series of spatters that
will travel along the wall or the ceiling. As the blood is being
cast onto the wall, it forms droplets that are elliptical in shape
and they’ll have long tails that point in the direction of travel.
That allows me to tell where in the room the crime took place.
“One pattern I remember in particular was a case where a
knife was the murder weapon. As a knife is swinging perpendicular
to a wall, the blood will come off both sides of the blade
at the same time and create these tiny little twin spatters that
are parallel to one another.”
As Kim explains it, there is a multi-step approach to looking
at evidence. For example, when she’s looking at a reddishbrown
stain on clothing, she does a presumptive test for blood
called the Kastle-Meyer test. The stain is swabbed and then a
drop of the Kastle-Meyer solution, which is reduced phenolphthalein,
is added to it. A second drop of three percent hydrogen
peroxide is added. If the swab turns pink rapidly, then it’s
positive for blood. If you’ve ever watched any of the CSI shows
on television, you’ve seen this test done numerous times.
There’s another test that takes it one step further that can
be used to determine anti-human hemoglobin, but, as Kim
explains with a touch of humor, “We can only call our
findings using this test as ‘consistent with human
blood’ because it cross-reacts with ferrets, although
we haven’t had many problems with criminal ferrets
in New Hampshire.”
When asked what gives her the
most difficulty at a crime scene, Kim
answers without hesitation. “When
I arrive at a crime scene, the body is usually already gone. I
can deal with almost anything, but sometimes the smell really
bothers me. The way I deal with it is to wear a paper mask with
strong perfume on it. There are times when I’ll have flashbacks
to the smell. If I’m at a scene and the smell is terrible, and then,
weeks later back in the lab, the clothing comes in from that
scene, I’ll get a most unpleasant flashback to the smell.”
Kim feels that one of the things that makes her job rewarding
is when she gets to think creatively and come up with an
important piece of the puzzle that will help solve a case.
One case in particular involved a young girl and an older
man who had assaulted her, but who had left no evidence on
the girl. However, shortly after the assault, detectives were
able to retrieve the suspect’s underpants, and, as Kim explains,
“I was examining them with an alternate light source we
call a crime light. That’s a light that shines at a blue-green
wavelength of around 450 nanometers. We use it to look for
the presence of body fluids on fabrics. As I studied the inner
waistband area of the underpants, I saw a faint fluorescence. It
struck me that it might be a transfer of the young girl’s vaginal
epithelial cells onto the suspect’s waistband. So, I took a
cutting of that and did a DNA analysis. What I had thought
turned out to be correct. By finding this trace evidence on the
criminal’s underpants, I was able to show that the girl’s DNA
ended up where it shouldn’t have been, which helped result
in a conviction.”
Among the other tools of the trade Kim uses are yellow
filter goggles that block UVA and UVB, the two spectrums of
ultraviolet light, and allow her to more easily identify
urine, semen, saliva, or sweat stains, and which stains
may be from some other fluid. Once Kim determines
what she believes the stain to be, she does a presumptive
test using various chemicals to pin down the
exact source of the stain. Finally, a cutting of the
stain may be sent for DNA testing.
One of the common tools Kim uses is a
biological microscope, but the new star of all the
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