1. LEVELED READER • X
Seeing the Evidence:
Forensic Scientists
at Work
Seeing the Evidence:
A Reading A–Z Level X Leveled Reader Forensic Scientists at Work
Word Count: 1,680
Written by Ron Fridell
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3. Introduction
A man walks quickly across a field into an old
mill, a building where wheat is crushed to make
flour. Inside the building, he murders someone
and then hurries away without being seen.
Later, when police questioned the man, he
insisted he was innocent. This suspect might have
gotten away with murder if only he had wiped
trace evidence off his shoes. Trace evidence
is dust, hairs, threads, and other tiny bits
of material found on or near a suspect or
victim of a crime.
When a detective named Edmond
Table of Contents Locard used a microscope to study the
man’s shoes, he noticed something
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
no one else had seen: traces of flour
Case File #1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 on the heels and soles. This trace
evidence matched the flour found
Case File #2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
at the mill where the victim
Case File #3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 was murdered. This placed
the man at the scene of the
Case File #4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
crime and helped to convict
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 him of murder.
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Traces of flour, right, could be seen on the
suspect’s shoes with a microscope, left.
3 4
4. The flour mill murderer was caught by Besides these tools of
forensic science, the use of science to solve crimes science, Holmes
and convict criminals in courts of law. Detectives used his powers of
began to use science to solve crimes around concentration and
1900. Before then, police used eyewitnesses and deduction to see
informers to solve crimes. what no one else
noticed. In A Case
of Identity, for
example,
Victorian Holmes and
boots, such his friend,
as those from
A Case of Identity Dr. Watson,
receive a
visit from a young lady who seeks their help in
solving a crime. Holmes comments that she must
have left home in a hurry, since her boots were
mismatched and not properly laced up.
Holmes’s deduction amazes Watson. Watson
wonders how he missed this detail about their
One of the first detectives to use forensic visitor. It’s simple, Holmes says, “You did not
science was a make-believe one, an Englishman know where to look, and so you missed all that
named Sherlock Holmes. The popular Holmes was important.”
stories and novels, written by Sir Arthur Conan
Doyle, started appearing in 1887. Most of the In the following four real cases, forensic
stories began in the fictional detective’s cluttered scientists, like Holmes, know where to look
London home, where shelves bulged with to spot important evidence. As you read, put
scientific reference books, and tables teemed with yourself in their place and test your own powers
test tubes and microscopes. of concentration and deduction.
5 6
5. How the Case Was Solved
Case File #1
Place: Oregon, U.S.A. The police asked for help from Edward
Date: October 11, 1923 Heinrich, head of the Berkeley, California,
Crime: attempted robbery forensic science laboratory. Heinrich was famous
of a train known as for being able to discover a great deal from very
the “Gold Special”
little evidence.
Evidence: a pair of men’s overalls
Heinrich told the
police to be on the
lookout for a left-
The Crime handed lumberjack
in his early twenties
The scene of the crime is a
weighing about 166
remote stretch of railroad track
pounds and standing
in southern Oregon. The year is
5-feet, 10-inches
1923. A Union Pacific freight train
tall. He also said the
has been robbed. The bandits
lumberjack had light
killed the engineer and used a
brown hair, rolled
homemade dynamite bomb to blow open the mail
his own cigarettes,
car. Back then mail often held valuable stock and
and was unusually
bond certificates and sometimes cash or gold.
Edward Heinrich works in his neat about his
When police searched the scene, the only piece of Berkeley crime lab.
appearance.
evidence they found was a pair of stained overalls
that one of the bandits had left behind.
C ase Fact!
The bandits actually used too much dynamite and
What could someone discover about blew up any money that may have been in the mail car.
you from examining your clothing? The explosion was so loud and destructive they ran from
What would it tell about you? the scene without having robbed anyone of anything.
7 8
6. right pocket left pocket And one more thing, Heinrich said, showing
police a piece of paper he had found rolled up at
the bottom corner of a pocket.
more The paper was bleached clean
wear
from many washings, but when
treated with iodine, words began
to appear. It was a receipt from
more
fraying a post office, made out to Roy Post Office receipt
D’Autremont of Eugene, Oregon.
Police went to Roy’s house and learned that
he was missing, along with his two brothers.
Just as Holmes amazed Dr. Watson, Heinrich Neighbors’ descriptions of Roy matched Heinrich’s
amazed the police. How could he have description exactly. When police tracked down
discovered all that from a pair of overalls? the brothers several years later, they confessed to
the robbery and murder and were sent to prison.
Heinrich explained: The fact that the left The railroad robbers case was just one of some
pocket was more worn than the right meant the 2,000 cases that Heinrich solved during his career
owner was left-handed. What stained the overalls as a forensic investigator.
was sap from trees that grow in southern Oregon
forests where lumberjacks work.
The overalls’ size told Heinrich the
lumberjack’s height and weight, and Tobacco
he could estimate the owner’s age from strands
a light brown hair caught on a button.
Tobacco shreds in a pocket
Single and nail clippings caught in
hair Nail
a seam told him the rest.
clippings Hugh D’Autremont Roy D’Autremont Ray D’Autremont
9 10
7. How the Case Was Solved
Case File #2
Place: Anyplace U.S.A. How could the police discover their identities?
Date: Anytime after 1950 The secret was on the thieves’ hands. Look closely
Crime: a series of burglaries at the tips of your fingers and thumbs, and you
Evidence: dirty dishes will see raised ridges of skin running in patterns
of curving lines: your fingerprints. Each of your
fingerprints is different from the other nine, and
The Crime each one is unique. No one else on Earth has
fingerprints like yours, and no one ever will.
Police believed that a
series of burglaries had In 1896, an
been committed by the Englishman
same gang of thieves. named
Finally, they discovered Edward Henry
where the thieves lived. discovered
The gang was one step a system
ahead, though. When to classify
Unwashed dishes
detectives raided their fingerprints.
apartment, it was empty. The thieves were gone. In 1901, he
became a police
The police searched the apartment, but they
commissioner and
could find no trace evidence. The entire place had
used his system to
been wiped clean, but not quite. The thieves had
identify criminals.
forgotten to run the dishwasher.
A forensic
What evidence could the police find scientist uses
black powder
in the dishwasher?
and a brush to find
fingerprints on a mug.
11 12
8. Criminals know this, and many are careful
Classifying Fingerprints to leave no fingerprints behind. When crime
Edward Henry based his system on features that every
fingerprint shares. Every print has ridges (the raised lines) and
scene investigators (CSIs) searched the thieves’
furrows (the low spots between ridges). And every print has apartment, at first they found no fingerprints.
arches, loops, and whorls. Arches are either tented (pointed It looked as if the thieves had carefully wiped
at the top) or plain (rounded). Loops are either radial (running the whole place clean, floor to ceiling. However,
toward the thumb) or ulnar (running toward the little finger).
the CSIs got fingerprints from the dishes in the
Whorls are circular.
Henry added smaller features to his system, known as forks,
dishwasher and matched them to prints in the
dots, islands, hooks, and bridges. All together, the type, number, database. The robbers were caught because of
and position of these features make each fingerprint unique. their dirty dishes.
Type 1 Type 2
arch loop
dots What
type of
Type 3 fork fingerprint
whorl
is this?
island
Henry’s basic system is still used today. Police
have about 50 million fingerprints in computer
databases. Prints found at crime scenes can
be compared quickly with all the prints in the
databases. When a match turns up, police have a
piece of evidence that places a person at the scene A technician uses a computer database to match fingerprints of
of a crime. suspects to crimes.
13 14
9. Case File #3
Place: Oklahoma, U.S.A.
Date: April 19, 1995
Crime: a federal building is blown up
Evidence: a truck axle
This part of a truck’s vehicle identification number gave
The Crime investigators evidence used to solve the bombing case.
The crime scene investigators
sometimes have only a small How the Case Was Solved
apartment to search. But Murrah Federal Building,
Oklahoma City After searching for days, investigators finally
sometimes the crime scene is
found a small piece of a truck’s axle. The rear axle
huge. In this case, the CSIs had several city blocks
belonged to the truck that carried the bomb. The
covered in thousands of tons of rubble to search
rear axle of every truck has a vehicle identification
for clues that would lead them to a suspect.
number (VIN) in the metal. This piece of axle had
At 9:08 on the morning of April 19, 1995, an only part of the VIN, but it was enough to lead
explosion rocked downtown Oklahoma City, investigators to a truck rental office in Junction
Oklahoma. A truck carrying a 5,000-pound bomb City, Kansas.
exploded, blowing away the front of the nine-story
The clerk remembered renting the truck to a
Murrah Federal Building. The blast killed 168
man named Robert Kling. The name was false, but
people and injured more than 500. The bomber set
the clerk remembered what the man looked like.
off the blast by remote control and drove away.
A forensic artist made a sketch from the
clerk’s description, and the owner of a nearby
How could a truck axle lead investigators motel recognized the face. The man had rented a
to the suspect?
room from him and had used the name Timothy
McVeigh.
15 16
10. Investigators ran the name through a national
Locard’s Exchange Principle
crime computer database and came up with Edward Heinrich did his work in a crime lab, a room
a match. A man by that name was being held filled with scientific equipment used to help discover and
on a traffic and weapons charge in the Perry, study forensic evidence.
Oklahoma jail—and was about to be released. The world’s first crime lab was set up in 1910 in
Lyons, France, by police detective Edmond Locard.
Investigators got there just in time. The Locard stated a guiding principle that today’s forensic
Oklahoma City bomber was caught, thanks in scientists still follow. He called it the Exchange Principle:
“Objects or surfaces that come into contact always
large part to the work of forensic investigators.
exchange trace evidence.”
Timothy McVeigh was later tried, convicted, and In other words, everyone who enters a crime
put to death for the bombing. scene takes away something from the scene and
leaves something of themselves behind. Locard, you’ll
remember, was the detective who solved the flour mill
murder case.
The forensic artist’s sketch, inset, led investigators to Timothy A forensic scientist works in a lab more modern than
McVeigh, above center. that of Edward Heinrich.
17 18
11. Case File #4
Place: England, U.K.
Date: 1993
Crime: armed robbery of $100,000
Evidence: a nylon stocking used
as a mask
The Crime
A view of skin under a microscope isn’t the same as a microscopic
The scene of this crime is picture that makes a DNA profile.
the office of a manufacturing
nylon mask no mask
company in England in 1993.
How the Case Was Solved
The $100,000 cash used to pay workers is in the
office when an armed robber breaks in and carries When the robber pulled off his mask back in
off the money. 1993, twenty-five of his skin cells came off with
it. In 2004, eleven years later, scientists were able
Crime scene investigators found no
to make a DNA profile from the stored skin cells,
fingerprints in the office. The only piece of
which led police to a suspect named Andrew
evidence left behind was the robber’s mask,
Pearson.
a woman’s black nylon stocking. Unlike the
overalls in Case No. 1, the stocking had no At Pearson’s trial in 2004, a forensics expert
pockets or seams where trace evidence could be showed that his DNA profile was an exact match
discovered. for the profile from the skin cells on the robber’s
mask. What were the chances that these skin cells
could have come from another person and not
What tiny bits of evidence might be left Pearson? A billion to one, the expert said.
on the stocking?
Pearson was convicted of the 1993 robbery and
sent to prison.
19 20
12. Conclusion
DNA Profiling
Modern scientists and engineers keep inventing new Each of the four cases in this book deals with
and better ways to gather forensic evidence. The most
a different kind of forensic evidence. There are
important new way is known as DNA profiling.
DNA is the part of each of your body’s cells that other kinds of forensic
carries instructions that tell your body how to live and evidence, too—footprints,
grow. About 98 percent of these instructions are the shoe prints, palm prints,
same in all people. The 2 percent that are different lip prints, bite marks, paint
make your DNA unique, just like your fingerprints.
chips, tire tread marks, the
Scientists can make microscopic, X-ray pictures
of unique DNA, known as DNA profiles. Police have markings on a bullet, and
tire tread marks more. Any of these can link
developed computer databases of DNA profiles, just
like fingerprint databases. suspects to the scene of the
DNA can be collected from almost any cell in your crime, or can show who
body, including cells in your hair, saliva, blood, sweat,
is innocent.
and tears. Police hoped to gather DNA evidence from
the robber’s stocking. They failed in 1993, but in 2004 bullet
Together, the law
things were different. DNA technology had advanced so
enforcement officers
that even a single skin cell could produce a DNA profile.
and scientists who
gather and study
forensic evidence
use virtually all of
the sciences, from
anthropology to
shoe print
zoology, in their
work. Whatever
science they specialize in, they all have one thing
in common. Like the fictional Sherlock Holmes,
they use their knowledge to see what goes
A computer is used to match DNA profiles. unnoticed by the rest of us.
21 22
13. Glossary fingerprints the unique patterns of ridges and furrows
on the tips of fingers and thumbs (p. 12)
convict to prove guilty of a crime (p. 4)
forensic the areas of science that apply to a court
crime lab place where scientific materials, such as science of law, often proving guilt or innocence
microscopes and chemicals, are used to (p. 5)
analyze forensic evidence (p. 18)
informers people who secretly give information
crime scene place where a crime has been committed about a crime, often for a reward (p. 5)
and where investigators look for evidence
to solve it (p. 18) microscopic so small that it can only be seen with a
microscope (p. 21)
crime scene law enforcement officer who investigates
investigator a crime scene to search for forensic suspect a person who is believed guilty of a crime
(CSI) evidence (p. 14) (p. 4)
deduction a specific conclusion made from general trace dust, hairs, threads, and other bits of
evidence (p. 6) evidence material used as forensic evidence (p. 4)
DNA deoxyribonucleic acid; a single molecule vehicle unique multi-digit number imprinted on
in a cell containing the instructions for identification a car or truck (p. 16)
growing and operating a living organism number (VIN)
(p. 21) victim someone harmed by an act or condition,
DNA profile X-ray photograph of a section of DNA such as a crime or war (p. 4)
that positively identifies the person it
came from (p. 20) Index
Exchange Edmond Locard’s idea that objects or crime lab, 18 Henry, Edward, 12, 13
Principle surfaces that come into contact always DNA, 21 Holmes, Sherlock, 5, 6, 9, 22
exchange bits of trace evidence (p. 18)
DNA profiling, 20, 21 Locard, Edmond, 4, 18
eyewitnesses people who have seen something happen
Exchange Principle, 18 McVeigh, Timothy, 16, 17
such as a crime or accident (p. 5)
fingerprints, 12–14, 19, 21 Oklahoma City bombing, 15–17
Heinrich, Edward, 8–10, 18 trace evidence, 4, 11, 18, 19
23 24
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