collect your own samples of hairs, threads, bits of cloth,
sand and other specks and study them with a hand magnifier.
If you wish to study your own clues further, a student
stereomicroscope is easy to use and you will see a lot more
detail than with a hand magnifier. Good student microscopes
can be bought from microscope dealers, specialty science
product shops and through the Internet. Some stores sell
used student microscopes. Never buy a microscope from a toy
store! The quality of the lenses is poor and you will not
be able to see your samples clearly. The price of a good
quality student microscope is similar to that of student
The Clue is in the Writing
Scientists are always comparing known things to unknown
things. Two pieces of evidence may look alike but may be
made up of totally different ingredients. This experiment
will help you tell the difference between inks that may look
alike, and match inks that are chemically the same.
Chromatography is a colorful way to identify chemicals in a
substance. Each different chemical looks different on the
coffee filters or white paper towels
markers of different brands and colors
several different black felt-tip and ink pens to
compare. Try to find two of each kind.
a strip of white coffee filter or white paper towel
measuring about one inch wide and six inches long for
Place a large black dot about one inch from the bottom
of each strip.
each strip into water to a level just below the dot.
Make sure the dot stays above the water.
Allow the water to soak up the strip and watch what
happens to the ink.
the strip out of the water and place it on paper. Above
the test strip, write down a number corresponding to
that strip of paper. On a separate sheet of paper
record which pens you used to make the dot on each
Repeat the experiment with the rest of the strips, pens
you have made all your test strips, see if you can match
up the pair made by each kind of pen. Check your
results against your record of the pens.
a friend write a note using one of the pens. Can you
identify which pen was used to write the note?
using different colored markers and pens. How do your
results compare? What colors make up green ink? Red
ink? Blue ink?
rainbow effects (chromatography results) are observed when
complex chemicals like ink are separated into the chemicals
from which they are made. The word chromatography comes
from chromato, which means “color” and graphy
which means “writing or arranging by a special means”. Inks
contain different chemicals that travel at different speeds
along a piece of paper.
The Clue is in the
scenes, police look for fingerprints left behind. Some
prints are visible like dirty hand prints. Most are
invisible, or latent, which means they cannot be easily
seen. In this experiment you will see how the Forensic
Scientist makes these prints visible in the laboratory in
order to compare them to the record fingerprints of the
victim and suspect.
Transparent tape, ¾ inch wide works the best
soft cotton ball or very fine paintbrush
powder, talcum powder or cornstarch
the side of the sharpened end of a pencil on a clean
sheet of white paper back and forth until a darkened
spot is made.
one fingertip over the pencil spot.
Place a strip of clear tape sticky side down on the
Carefully remove the tape from your finger and stick to
another clean sheet of white paper. The print should
clearly show the ridge patterns of the fingertip. This
may take some practice.
Repeat until each fingerprint is in place. You may need
to rub the pencil point again between each fingerprint.
your hands then label each print in your fingerprint
record with the name of the finger it came from - for
example: LT = left thumb, LI = left index finger, LM =
left middle finger, LR = left ring finger, LP = left
pinky finger. Use R instead of L for the right hand
the same method to create record fingerprints of your
family and friends.
Compare all of the fingerprints using a magnifying
glass. How are the similar? How are they different?
someone make mystery fingerprints by first rubbing their
fingers on their oily forehead or rubbing cooking oil in
to their fingertips. They then press their fingers on
smooth objects like dinner plates, drinking glasses or
Choose a contrasting powder to dust the print - baby
powder, talcum powder or cornstarch for dark surfaces,
black pencil powder (made by rubbing a pencil tip with
sandpaper) for light surfaces. Carefully place some
powder onto the surface near the print. Next using a
feather, cotton ball or paintbrush gently brush the
powder across the print in both directions.
lift the print using transparent tape and place it onto
a piece of paper that contracts in color with the
Compare the lifted prints to your record fingerprints.
Can you identify who made the mystery fingerprints?
us is born with a distinct set of fingerprints. If you look
closely at your fingertips you can see these tiny raised
lines, called friction ridges. Fingerprints can confirm the
identity of a person. Fingerprints can be used to compare a
suspect in custody with evidence found at a crime scene or
with those of a known criminal whose fingerprints are on
The Clue is in the Dirt
dust can be important evidence in an investigation. When
all of the testing and observations are completed, it is
possible for a Forensic Scientist to supply valuable
information to indicate a likely source of this trace
evidence. In this experiment see how dirt and dust can be
used by a Forensic Scientist to solve a crime.
Dirt/sand/dust from different locations
Collect dirt from different locations, for example your
yard, playground, forest preserve. Place the sample in
a plastic bag and label each bag with its location.
Place a sample from each bag on separate sheets of white
Examine each sample with a magnifying glass.
Observe different characteristics of each sample – for
example: color of each sample, moisture content (wet,
dry, damp), size of the grains, stones or pebbles, plant
material, bugs or insect activity? Make a chart to
record your results.
are the samples different? How are they alike? Can you
tell what plants may be close by?
the same experiment using sand collected from different
the same experiment using dust collected from different
rooms and different households.
samples are mixtures of mineral, animal and plant origin at
various levels of change and decay. Many of the components
are common. Physical characteristics, such as color and
particle size can be important. The size of the soil
particles determines whether soil is sand, silt or clay.
Sand has the largest soil particles and clay has the
smallest. The great variations of these combinations lead
some to believe that soil has a unique composition in any
given area and changes detectably every few feet.
actually a collection of particles. It is a product of rock
erosion by a number of processes like wind, water and
glacial grinding. The natural occurrence of sand throughout
the world in a wide variety of forms can provide an endless
source of samples for the microscopist.
samples contain combinations of trace evidence from the
rooms where they were gathered. Dust can consist of human
and animal hairs, fibers, dirt, sand, paint particles,
plants, insect parts and any other items that the
surroundings might contribute.
this information can be used to study dirt and dust samples
found at a crime scene. Dirt and dust are common as trace
evidence because they are easily carried from the scene of a
crime in the soles of shoes, on clothing or on the tires of
a vehicle. These materials can reveal important clues to
suggest a person’s occupation or workplace or where they
have recently traveled. Forensic Scientists compare the
dirt and dust found at a crime scene with selected samples
to determine where they may have come from.
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