AOW DUE: DECEMBER 14, 2012 Name: _________________
Cool Jobs: Crime scene investigators
These researchers don’t miss a clue
article from: http://www.sciencenewsforkids.org/2012/12/cool-jobs-crime-scene-investigators/
By Sid Perkins / December 5, 2012
The dead do tell tales — if experts care to listen. Forensic
anthropologist William Bass arranges a display of how a person’s
bones change year by year as we age. This information can help
identify a crime victim when little else is known. Credit:
University of Tennessee, Knoxville
This is one in a series on careers in science, technology,
engineering and mathematics made possible by support from the Northrop Grumman Foundation
TV shows such as CSI: Crime Scene Investigation and Bones make forensics look exciting — and in many
cases, using science and technology to investigate crime is exciting.
Some crime scenes come loaded with clues: fingerprints, bullet holes, blood spots and even a body or two.
Others have almost none: Maybe just a small swath of an escapee’s clothing snagged on a fence or a tiny scrape
where a burglar jimmied a window. In still other cases, the clues can be so minuscule that they require a
microscope to reveal.
If anything, television shows make solving crimes seem easier, more glamorous and certainly quicker than in
reality. “Those shows are mostly just for entertainment,” says Kendall Stoner, an analyst at the Tennessee
Bureau of Investigation’s crime laboratory in Nashville. “We only have basic computers, and our lab doesn’t
look like a movie set,” she says. “But we get the job done.”
Here we profile Stoner and two other real forensic experts. Each job requires very individual skills, yet all three
work in teams to decipher crime scenes, identify evidence and help bring criminals to justice. Oh, and these
specialist crime fighters also help ensure no innocent people are punished for crimes they didn’t commit.
“It’s all about making sure that the correct person is prosecuted,” says Reanna Day, an agent with the Federal
Bureau of Investigation in Knoxville, Tenn.
On the scene
Arson, bank robbery, kidnapping and murder are just a few of the many
serious crimes forensic experts will investigate. These crimes can happen just
about anywhere, from the tallest office building to the deepest forest. Solving
such a diverse set of offenses across a range of scenes is challenging. But
there’s good news: “Anything can be a piece of evidence,” Day points out.
Researchers at the University of Tennessee’s Forensic Anthropology Center, nicknamed the Body
Farm, excavate the site of an experimental burial to learn more about how the human body
decomposes. Credit: University of Tennessee, Knoxville (Photo Caption)
Day leads one of the response teams that the FBI trains to probe for clues at crime scenes. While Day studied
Japanese and math in college, the FBI Academy in Quantico, Va., taught her the science of collecting evidence,
including hair and carpet fibers. “These are things that can disappear or be tracked from one part of the crime
scene to another if you’re not careful,” she notes. She also learned how to collect and preserve fingerprints, as
well as samples of blood.
Photographs are an important part of Day’s job, since they document exactly how a crime scene looked before
her investigating scours the site for evidence. Later, this scene-setting information helps analysts interpret that
evidence, which law-enforcement agents also use to identify suspects. Eventually, attorneys rely on that same
evidence to help show a suspect’s guilt or innocence.
Examining a crime scene can take 12 or more hours. It might involve poring over a single room for a handful of
clues — or a broad patch of forest laden with thousands of potential clues. Day and her team sometimes work
quickly. “If it’s raining or snowing, we have to rush to protect evidence before it gets erased,” she notes. Other
times, at the scenes of crimes that occurred outdoors long ago, the team works at a careful pace familiar to any
archaeologist.
Day and her response team are real evidence sleuths. They find and collect physical clues. They then leave the
analysis to experts with other types of specialized training.
Meanwhile, back at the lab
The job of the crime analyst is to study evidence collected at a crime scene. Often, that means comparing
evidence to information contained in huge databases. Those databases contain everything from the treads of
thousands of different sneakers, boots and other footwear to millions of fingerprints. Making a match can help
identify clues and nab criminals.
In recent years, DNA analysis has become one of the greatest forensic tools for identifying crime suspects. For
Kendall Stoner, it is every bit as important as the magnifying glass was a century ago.
About 99.8 percent of human DNA is identical among all people. However, the remaining 0.2 percent contains
enough differences to give each person a unique genetic signature. (Except in identical twins, and even then
there are individual differences in the chemicals attached to their
genes.)
Many detectives call a DNA profile a “genetic fingerprint.” That is
because just like an actual fingerprint, a suspect’s unique DNA also can
provide a link to a crime scene.
DNA analysis is like the puzzles (and crime novels) that Stoner loved
as a teen. “Anything where I was working toward an answer,” Stoner
says. “I loved the challenge.”
A vial contains a cotton swab used to collect DNA evidence at a crime scene. A person’s DNA provides a genetic fingerprint unique
to every individual. Credit: FBI – Photo Caption
Even before Stoner went to college she wanted to work in law enforcement. At the University of Alabama in
Tuscaloosa, she also became interested in genetics and earned a degree in biology. Later, she received a
graduate degree in forensic science, this time from the University of Alabama in Birmingham. Today, Kendall
is one of 10 DNA analysts at the Tennessee Bureau of Investigation’s crime lab in Nashville.
Kendall Stoner performs some genetic sleuth work in her laboratory at the Tennessee Bureau of
Investigation’s crime lab in Nashville. Credit: Tennessee Bureau of Investigation (photo caption)
For each analysis, Stoner starts by collecting DNA from evidence collected at a
crime scene. She might swab a bloodstained piece of clothing or snip a piece of
skin collected from under a victim’s fingernails — skin that may have been
scratched from a suspect while fending off an attack.
Stoner then drops the swab, and any cells it has picked up, into a test tube
holding a chemical solution. That solution extracts the DNA from the cells. Next,
she adds dyes that reveal whether there’s enough DNA present to produce a
genetic profile. If there is, she uses a process called polymerase (PO lim er AZE)
chain reaction, or PCR, to copy the DNA over and over. PCR can take just onebillionth of a gram of a person’s genetic material and create thousands or
millions of copies of that DNA. Finally, Stoner places this amplified — or
copied — genetic material into a machine that converts genes in the DNA into a
series of numbers. These numbers can be compared to other DNA profiles.
Stoner often mixes her own chemical solutions: The fresher they are, the better the results, she notes. While
Stoner falls back on the science she learned in school, she also constantly learns new skills. That is because the
science of DNA profiling is evolving so quickly, there are always new tricks of the trade to learn. The tradeoff?
New developments in chemistry and technology now let Stoner produce genetic fingerprints from smaller
amounts of genetic material than ever.
Even in the fictional world of television, Stoner notes characters often are shown using real forensic techniques.
Still, these crime shows can give viewers some wrong ideas. For instance, Stoner says, “one cell doesn’t
provide a full DNA profile. Also, you can’t collect DNA off of just anything.”
Last year, Stoner and her fellow DNA analysts in Nashville performed about 10,000 DNA tests on almost 5,700
pieces of evidence. “You’re always learning something, and every case is different,” Stoner says. “If you want
to sit behind a desk and do the same thing day after day, this is not the job for you.”
E-I, E-I … oh!
While investigators discover some murder scenes very quickly, they may not find others for weeks, months or
even years. By then, all that’s left of a victim might be a bare skeleton. Determining a victim’s identity, much
less how and when he or she died, poses a challenge.
In such cases, investigators often turn to forensic anthropologists like William
Bass, of the University of Tennessee in Knoxville. Bass and other experts often
can identify victims even after they have been burned, mutilated or left to rot. For
example, the length of the leg’s femur can reveal how tall a victim was. The shape
of the pelvis can indicate a victim’s gender. Even the skull can provide clues
about a victim’s gender and race.
William Bass unearths a crime victim’s decomposed remains as law enforcement officers look on.
Credit: The University of Tennessee, Knoxville (photo caption)
In many cases, Bass says, the best clue to identifying a victim can come from
pinning down when the person died. Even a range of dates can let investigators,
relying on reports of missing persons, narrow the list of possible victims. It also
can help support or refute the alibis of murder suspects.
Before the 1970s, estimating a victim’s date of death was more guesswork than science. “No one had really
scientifically studied how bodies decompose,” observes Bass. So no one knew the answers to some simple —
but grim — questions, such as: When do the teeth begin to fall out of the skull? At what point do the arms
detach? What causes the greasy black stain beneath decomposing bodies (and how long does that last)?
In 1980, in an attempt to find some answers, Bass and another colleague at the University of Tennessee founded
what’s now called the Forensic Anthropology Center. Today it is better known by its nickname: the Body Farm.
Corpses that end up at this 1-acre plot of land, alongside a river near the university’s downtown campus, aren’t
crime victims. Instead, the bodies — what physicians refer to as cadavers — have been donated to science.
Each cadaver is a separate science experiment. The Body Farm’s cadavers include males and females of all
ages. Researchers leave some cadavers lying in the sunshine on open ground; others they place in the shade
beneath trees. Some are clothed, others naked. Leaves and branches cover some bodies. Others are buried in
shallow graves — or even under a concrete slab. Some bodies are left to decompose in small sheds or buildings,
while others are left in the trunks of cars. “There are thousands of possible variations, and we’re studying only a
few,” Bass says.
Each variation reproduces a certain type of crime scene. By studying all aspects of body decomposition, over
long periods, the researchers have compiled a wealth of data that law enforcement analysts can use.
Not surprisingly, bodies quickly decompose in summer, Bass says. “They can go from fresh body to a complete
skeleton in only two weeks,” he notes. Maggots, or the larvae of blowflies, play a big role. These insects (Bass
calls them “nature’s little helpers”) can swarm a body by the hundreds within minutes. “They’re the first insects
to attack a body,” Bass observes.
In an FBI laboratory, an analyst swabs a plastic bottle for DNA. The genetic
material can help identify a crime’s victim — or its perpetrator. Credit: FBI
But blowflies aren’t active at temperatures below 52°F (11.1°C). So during
cold weather, decomposition slows dramatically. “You can leave a body out in
November, and it can still be in pretty good shape until April or so,” the
researcher says.
As gruesome as the work is, it’s still science. Bass and his colleagues use biology, anatomy, chemistry,
entomology (the study of insects) and anthropology (the study of humans and their culture) to unravel each
case.
“This is an interesting field, if you like puzzles,” says Bass, who is now retired but still collaborates on research
projects.
Whatever the particular job, the challenges of finding answers makes forensics an interesting career for the
curious. There is also the reward of helping fight crime — something Day, Stoner and Bass all say motivates
them too.
Power Words
forensics The use of science and technology in investigating crimes.
anthropology The study of humans, their culture and sometimes the evolution of their physical traits.
arson The crime of intentionally setting a fire with the intent to cause damage.
cadaver A human corpse.
database An organized collection of information.
decomposition The process by which organic materials, including animal remains, break down over time.
DNA (Deoxyribonucleic acid) A molecule found in nearly all cells of all living organisms. This genetic
material contains the instructions needed for the organism to develop, function and reproduce.
DNA fingerprint The unique set of genetic markers that identify an individual.
polymerase chain reaction (PCR) A biochemical process that repeatedly copies a particular sequence of DNA.
maggot The larva of a fly.
MONDAY, DECEBER 11, 2012
1. Why do you think the FBI training facility is nicknamed the Body Farm?
A.
B.
C.
D.
Because the FBI trainees learn how a body decomposes over time
Because the FBI trainees create different crime scenes
Because the FBI thinks it is a cool name
Because the FBI wants to scare people away from Quantico
2. What are some of the skills that Day learned at the FBI training facility in Quantico?
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3. Why are crime scene photographs important? _________________________________________________
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Tuesday, December 11, 2012
4. Human DNA is an important part of a crime analyst’s job. Why? __________________________________
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5. What are the steps that Kendall Stoner takes to analyze DNA from a crime scene?
She obtains the DNA evidence
from a crime scene (maybe from
under fingernails, or from a
victims clothing.
She adds a dye to the test tube to
determine if there is enough DNA
present to make a genetic profile.
She puts the replicated (copied)
DNA into a machine that turns
the DNA into a series of numbers
6. Stoner then drops the swab, and any cells it has picked up, into a test tube holding a chemical solution.
That solution extracts the DNA from the cells. Next, she adds dyes that reveal whether there’s enough
DNA present to produce a genetic profile. If there is, she uses a process called polymerase (PO lim er
AZE) chain reaction, or PCR, to copy the DNA over and over. PCR can take just one-billionth of a gram
of a person’s genetic material and create thousands or millions of copies of that DNA. Finally, Stoner
places this amplified — or copied — genetic material into a machine that converts genes in the DNA into
a series of numbers. These numbers can be compared to other DNA profiles.
After reading this paragraph, determine the text structure (remember text structure is how the paragraph is
written –description, sequence, cause and effect, problem and solution, compare and contrast) What is the text
structure of this paragraph and how do you know? What signal words were used to help you determine the text
structure? (four points)
Wednesday, December 12, 2012
7. What are maggots and why are they important to a crime scene investigation? ________________________
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8. Complete the table about the three scientists that were the subject of this article and what each of them does
to help solve crimes.
Kendall Stoner
Trains students to look for
and collect clues at a crime
scene
William Bass
10. What happened in 1980 to help scientists solve crime, and how did this help crime scene investigators solve
crimes? __________________________________________________________________________________
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11. What types of sciences are involved in solving crimes? _________________________________________
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12. Do you think you would like to become a crime scene investigator? Why or why not – use evidence from
the selection to support your opinion.
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