Who took a bite out of the candy? Sticky fingers have been found on the broken
aquarium glass. Wet footprints lead to the open window. What is that powdery
substance next to the broken piggy bank? Answering these questions is what
forensic science is all about.
Forensic science is the study of objects that relate to a crime. The objects are
evidence and analyzing the evidence is what forensic scientists do. They
observe, classify, compare, use numbers, measure, predict, interpret data, and
draw inferences. Scientists they are and crimes they solve.
Learn how to be a crime solver by exploring the world of the forensic scientist.
Before studying a crime scene we must practice the skills needed in analyzing
evidence. After you have completed the skill building assignments, try solving the
Why Fingerprint Identification?
Fingerprints offer an infallible means of personal identification. That is the essential
explanation for their having supplanted other methods of establishing the identities of
criminals reluctant to admit previous arrests. Other personal characteristics change -
fingerprints do not.
People have noticed subtle differences in fingerprint patterns for centuries. The following
websites illustrate this history. Browse the four sites listed and answer these questions.
In ancient Babylon, fingerprints were used on clay tablets for business transactions, but it
is doubtful that people used this for identification.
In 14th century Persia, various official government papers had fingerprints (impressions),
and one government official, a doctor, observed that no two fingerprints were exactly
In 1686, Marcello Malpighi, a professor of anatomy at the University of Bologna, noted
in his treaties; ridges, spirals and loops in fingerprints. He made no mention of their value
as a tool for individual identification. A layer of skin was named after him; "Malpighi"
layer, which is approximately 1.8mm thick.
In 1856, Sir William Hershel, Chief Administrative Office, Bengal India, first used
fingerprints on native contracts.
In 1880, Dr. Henry Faulds, who was working in Tokyo, Japan, published an article in the
Scientific Journal, "Nautre" (nature). He discussed fingerprints as a means of personal
identification, and the use of printers ink as a method for obtaining such fingerprints. He
is also credited with the first fingerprint identification of a greasy fingerprint left on an
In 1883, in Mark Twain's book, "Life on the Mississippi", a murderer was identified by
the use of fingerprint identification. In a later book by Mark Twain, "Pudd'n Head
Wilson", there was a dramatic court trial on fingerprint identification.
In 1892, Juan Vucetich an Argentine Police Official, made the first criminal fingerprint
identification. He was able to identify a woman by the name of Rojas, who had murdered
her two sons, and cut her own throat in an attempt to place blame on another. Her bloody
print was left on a door post, proving her identity as the murderer.
1902, First systematic use of fingerprints in the U.S. with the New York Civil Service
Commission for testing. Dr. Henry P. DeForrest, a pioneer in U.S. fingerprinting.
Back in 1908, there were different crimes than what we have today. Also, there
were far fewer types of crimes than we have today. A good example of this is car
theft. In 1908, almost no one had a car, but as more people bought cars, the
number of car thefts increased.
There are over 250 million sets of fingerprint records on file. If all of the
fingerprint cards on file were stacked on top of one another, they would equal
one hundred and thirty three stacks, each the size of the Empire State Building!
Finding space to keep all of these fingerprint cards is difficult! This is one of the
reasons that the FBI is now putting the cards in digital format so that the images
can be stored on computers. They even have mine!
Remember - fingerprints are unique. Not even identical twins have the same
fingerprints. Take a minute to look at your own fingertip and notice all the ridges
and swirls. Now, look at your parents' fingertips. Can you tell the difference?
Take a minute to look at the seven different fingerprint patterns that are used to
identify people. You can compare your own fingerprints to these patterns and see
which one looks most like your own!
There are other ways of telling people apart besides fingerprints. Did you know
that each of us is made up of millions of cells and inside those cells are particles
called DNA? It is everywhere in our bodies, including in our hair, blood, saliva,
skin, and bones. These particles make up a code that is used to tell people apart.
Identical twins share DNA coding, but they are the only people who do. This
makes DNA an excellent way of telling people apart. It has become a very
important tool in solving crimes when no fingerprints can be found.
Another tool that helps law enforcement solve cases is a polygraph. This
instrument is used to measure how a person's body reacts to questions. It is
based on the theory that a person's body will indicate if he or she is telling the
truth. Researchers John Larson and Leonard Keeler developed this machine
which is also known as a "lie detector."
You know how important it is to eat well and exercise, right? Your life depends on
it! For FBI Special Agents, it is no different. They must be in shape and they
must pass tests that check their physical skills, or they can't become Agents!
Cryptanalysts study secret messages. They know how to break codes like this
one that was found on a spy's laptop computer. Print this page and help break
Divide into groups of 2
Rub a pencil over the central part of an index card until it is covered
Use the second card for recording your prints. Write your name on
the lined side and turn it over.
Your will be making prints of the index finger and the middle finger of
the same hand. Begin by asking who is right- or left-handed and use
Note: You want to make prints not of their fingertips but of the pads
of their fingers, near the joint crease, because that is where the
most interesting patterns are.
To use the graphite pads, press and roll your finger firmly on the
penciled area, then stick a short piece of tape to the finger pad area,
pressing down thoroughly, remove the tape and press it onto your
print record card.
Immediately label your print "L" or "R" for left or right hand and "I"
or "M" for index or middle finger.
Repeat procedure for the second finger. Do it over until you get two
After all prints are made and labeled, compare your prints for
similarities and differences. Record your results in your lab notebook
o Are the two prints from the same hand more alike than prints
from different people? How? Record
o What are the positions of those patterns on the finger (how
close they are to the joint line)? Record
o What kinds of patterns do they see? Give names to the
patterns (circles, triangles, curvy lines) Record
o In which direction do the loops curve—toward the thumb or
toward the pinkie finger? (Remember that taped prints are like
looking at your finger palm-up and inked prints are mirror
images. It may be easier to ask whether they curve toward the
right or left of the card.) Record
o Compare the size of those patterns (such as how many ridges
make up a loop). Record
After you have compared and named your prints, look at the handout
with examples of "official" names for patterns (loops, whorls, and
arches). Record the official name of your prints in your Lab note
Get with another Lab group and classify your prints according to the
Pass your prints to another group and see if they agree with your
Get the results from the other groups. Which is the most common
pattern? Make a bar graph of your results in your lab notebook.
Note that, while scars, such as the white line on one of the sample prints in
this lesson, are the easiest patterns to see, they cannot be used either for
classification or identification. They are not unique in the way that ridge
patterns are, and they also change over time—making them unreliable for
Fingerprints at the Crime Scene
Now that you have classified fingerprints, how can they be identified when found
at a crime scene?
Fingerprints must be removed and transported to the crime lab. They are then
compared to the database of fingerprints on file. One way that detectives locate
fingerprints is by dusting for them. Fingerprints are coated with powder, then
lifted and taken for identification at the lab.
Try your hand at being a detective by dusting for fingerprints. You will need the
materials listed on the right.
Small soft brush (soft camel hair or fiberglass)
5 sheets of light-colored construction paper
1. When fingers are oily or sticky you get better fingerprints. So press
an oily or sticky finger on the side of a drinking glass.
2. Coat the fingerprints with a dusting of cocoa powder.
3. Brush gently with either a camelhair or fiberglass brush. The
4. Place the sticky side of the tape on the dusted fingerprint. Lift on the
tape and place on light colored construction paper.
Talcum powder should be used on dark surfaces.
The dusting method is used to lift prints from hard surfaces. Lifting prints from
smooth surfaces requires chemicals.
WHAT IS THAT WHITE POWDER?
A forensic scientist may discover powder at a crime scene. In order to determine
if it is illegal or not the crime lab will identify the substance using chemistry. Take
on the role of a forensic chemist to identify unknown substances.
The following materials will be necessary for your investigation:
Pencil White Chalk
Sheet of white paper Magnifying glass
Measuring spoons Eyedropper
Baking Soda Water
Sugar 4 small jars
Salt Iodine Solution
Cornstarch Dish Towel
4 sheets of back construction paper Vinegar
Become a Forensic Chemist by following these procedures and filling in the
Powder Analysis Chart with your results. See the chart (html file).
Complete the appearance, texture, and smell activities before opening the
vinegar and iodine bottles.
1. Place one-fourth teaspoon (1 ml) of the four white powders on a sheet of
black construction paper. Label the powders with the white chalk or white
2. Study the powders with the magnifying glass. Examine what each powder
looks like. How would you describe the powder's shape. Does it have
large or small grains? Your observations should be written in the
appearance column of the chart.
3. Examine the powders further by rubbing each powder between your
fingers. Describe how each powder feels in the Texture column of the
4. Determine if there is a smell to any of the powders. Record your findings
in the Smell column of the chart.
5. Take the eyedropper and place a drop of water on each individual powder.
Examine what happens? Do the powders dissolve? Is there a reaction?
Write your observations in the Reaction to Water column.
6. Place one-half teaspoon (2ml) of each powder in a separate jar. Add 2
drops of iodine to each jar using the eyedropper. Record what happens in
the Reaction to Iodine column. Iodine should be handled with care.
Comparing test results of substances that are known help Forensic Scientists
identify unknown substances.
After analyzing and recording results of each substance have your partner leave
the area. Select and place one of the powders on construction paper and do not
tell which substance it is. Invite your partner back to see if she/he can determine
the powder by performing the same experiments and observations previously
done. Change places so your partner can select one of the powders for you to
identify. Can you correctly identify the mystery powder?
Extension: View the powders under a microscope.
DENTAL FORENSICS OR THE TEETH CAN TELL
Forensic dentists assist in crime solving by studying teeth and teeth impressions.
Dental records are often used to identify people. Because teeth are one of the
hardest substances in the human body, they are frequently well preserved.
Dental x-rays or records showing fillings, position of teeth, etc. can help forensic
dentists find a match of teeth to the individual. Eighty percent of the time teeth
impressions are used to identify unknown victims.
As a forensic dentist you will have the chance to match teeth impressions to
discover who took the bite?
The procedures for making teeth impressions are:
1. Divide the styrofoam plate into six equal wedges. Cut the wedges.
2. Take two of the wedges and stack them together. Cut off 1 inch from the
pointed end of the wedges.
3. Place the two wedges into your mouth as far as possible.
4. Bite down on the wedges firmly and then remove them.
5. Label the top and bottom wedges Top Teeth and Bottom Teeth.
6. Study the teeth impressions. Count the number of teeth in the top and
bottom impressions. What other characteristics of the impressions do you
notice? Compare the top teeth impressions to the bottom. Are there teeth
missing, spaces, chips, etc.?
Practice being a forensic dentist by leaving the room. One student in the room
will take a bite of thick cheese or thick chocolate. See if you can identify the
individual who took the bite by comparing the impressions with the bite in the
cheese or chocolate.
THE FEET CAN MEASURE THE HEIGHT
The bones of the feet can tell a lot about a person. What do feet reveal about a
person's height? Forensic anthropologists team up with law enforcers to help
Bones of the feet can reveal an interesting fact about an individual. Let's combine
math with forensics to see how.
Create a spreadsheet.
List the individuals name, height, and foot length.
1. Have some adults remove their shoes and measure their height.
2. Measure the length of the adult's left foot from the wall to the tip of the big
3. Examine the numbers. Do you see a pattern?
4. Divide the length of each person's left foot by his/her height. Multiply the
quotient by 100. What do you get? You may also want to use the
calculator on a computer for this activity.
The results of your calculations should be about 15, illustrating that the length of
a person's foot is approximately 15 percent of his or her height.
Find out the approximate height of each of your classmates by measuring their
foot and charting it on a spreadsheet. Use this proportion for your calculations:
15/100 = Length of Foot/x (person's height)
When a forensic scientist has the length of a foot, the forensic scientist will be
able to approximate the height of the individual. This works best on a full grown
individual for the ratio of body parts is slightly different in growing children.
Click on objects in the picture to view clues.
At approximately 7:15 a.m., Friday morning, Mrs. King, the seventh grade
science teacher, thought something was fishy as she walked down the hall and
noticed that her door was open. She walked into her classroom and immediately
discovered that the small aquarium had been broken and her prized gold fish
were gasping in the sink. Beside the broken aquarium were the shattered
remains of the pink piggy bank that had been on the shelf above the aquarium. A
can of blue paint was spilled on the floor. Footprints of a barefooted burglar led to
an open window. Bits of a white powdery substance were found next to the
broken, empty, piggy bank. The only other item found was a half-eaten large
chunk of chocolate candy.
When the police arrived they immediately began to gather forensic evidence.
Sticky fingerprints were lifted from the aquarium and piggy bank.
The painted footprints were measured.
The chunk of chocolate candy was collected for examination. It appeared
there were teeth imprints.
The white powdery substance by the piggy bank was carefully placed in a plastic
bag and taken to the forensic chemist for identification.
Using the clues found at the crime scene, determine which of these four suspects
is the "barefooted burglar"? What do you think was the motive for this crime?
Write the results of your findings and convince a jury of your peers.
Suspects: Lou Lou, Dan the Man, Peg the Leg & Jake the Jock
Alias: Sweet Tooth
Lou Lou is so addicted to sugar that she never leaves home without it. She loves to bake
sweet things and has an entire pantry full of sugar bins. She claims to have been baking
her famous chocolate chunk cookies the morning of the crime (although not a morsel of
cookie or chocolate chunk was left when the police arrived.) Lou Lou rarely wears shoes,
which often causes her to slip and break things, especially her collection of ceramic pigs.
Dan the Man
Height : 5'8"
Alias: The General
Dan was wearing a woolen general's uniform with small holes when apprehended in
the woods. He claimed to be gnawing on wood for moisture and insects to practice his
survival training. His teeth look like a beavers from gnawing. His wife complains that
she never has any baking soda due to Dan's compulsion about storing clothes in
mothballs. He thinks the baking soda takes away the mothball smell, so he stuffs his
pockets with the substance. Also, his wife reports that her giant chocolate kisses
continually disappear from the candy cupboard. He blames their dog Patton, an
English bull terrier, who patrols the neighborhood. His neighbors report that Dan loves
the military. He was very regimented about playing taps on his bugle every day at
sunset until an irate neighbor broke his bugle. Dan has been trying to save money for a
Peg the Leg
Alias: Lucky Lady
Peg is a librarian known for hanging horseshoes and four leaf clovers in her library.
Employees say she is so superstitious she insisted on carpeting in the library instead of
laying tiles so she would not step on the cracks. She wraps construction zone tape around
open ladders so no one can walk under them. Cola bottles litter her office, which she
drinks with chocolate chunks. Her teeth are chipped from knocking the bottles against
them. She is always throwing salt over her shoulder for good luck and keeps a salt shaker
in her purse. Her alibi is that she was busy closing open umbrellas the morning of the
Jake the Jock
Alias: Armchair Quarterback
Jake the Jock is known for quoting statistics on every sport from boomerang throwing
to sled dogging. His neighbors report that he is the neighborhood pitcher for baseball
games. Last year a baseball hit him in the mouth and knocked out his front tooth. This
has cramped his eating style of chocolate chunks, candied apples, and corn on the cob.
His wife claims that on the morning of the crime Jake was rubbing his hands with
cornstarch to keep them dry in preparation for an important baseball game.