PART 2 OF EVIDENCE AND INVESTIGATION
HIGHLIGHT any key terms/concepts and important information 
Topic: Fabric and thread analysis
Thread
Thread can be made from two sources- Man made (synthetic) or natural.
Matching color from a thread to a fabric is the easiest way to find a match
Synthetic fibers: polyester, nylon, and plastic
Natural fibers: Cotton, silk, and wool
The most common way to weave thread is with an automated loom that interlocks
thread horizontally and vertically. Other common ways include knitting or braiding,
as seen in wool or other thick threaded fabrics.
Fabric
To figure out what kind of fabric we have, there are four tests we can do:
1- Absorbency test: how much water the fabric can absorb
2- Burn test: if the fabric melts or burns
3- Elasticity test: how much the fabric can stretch
4- Wrinkling test: how much the fabric wrinkles after being folded
Topic: Fingerprints
Fingerprint specialists use tools like big fluffy brushes, powder, tape, and
magnifying glasses to collect prints from weapons or anywhere within a crime
scene.
Dusting for prints means that the expert is dabbing a fine powder with a fluffy brush
to help reveal latent prints.
Latent fingerprints are not visible to the naked eye (ex: if you look at your
computer screen, it may look clean until you hold it in the right light)
Visible fingerprints are easy to see- the fingerprint may be covered in dirt,
powder, or a liquid that makes it easy to see (ex: your own fingerprints we did in
class with graphite powder)
Some of the difficulties faced in collecting fingerprints are that they may be
smudged or overlap with other prints. This means that we will not be able to tell
what kind of fingerprint it is.
The surfaces fingerprints are left on are important too! A surface that is rough,
uneven, or bumpy will not allow for prints to appear clearly, or we might only
get a partial print (ex: a basketball). Surfaces that are smooth and flat allow for
clear fingerprints to appear (ex: most appliances in the kitchen and glass)
Topic: Handwriting
There are many factors to compare when doing a handwriting analysis:
• Loop of letters
• Cross of “t” and dotting of “i” or “j”
• Space between letters and words
• Size of letters
• Slant/ angle of letters
• Pressure left on the paper
We need to look at all of these things to figure out if a sample of writing matching
the writing of a suspect.
Topic: Chromatography
Chromatography: separation of the ink of a pen or marker to see which colors have
been combined.
When we separate the colors used in ink, we saw that there are many different
combinations of colors that can be combined to make black ink.
We also saw that colored pens, like the green, are made up of other colors too! The
only ink that is not made up of lots of colors is permanent or dry erase.
Topic: Fair tests
Variables: anything that can be changed
Manipulated/independent variable: a factor that is changed regardless of the
constant variable (what is “different” or “changed”)
Constant/controlled variable: a factor that is NOT changed throughout the entire
experiment (what is the “same”)
Fair test: changing only one factor at a time while keeping all others the same. This
lets us see how that one change affects the overall experiment
PART 1 OF EVIDENCE AND INVESTIGATION
Topic: Tire tracks and tire tread
Tire tracks
Tire tracks focus on the information we can learn by analyzing two or more tires.
For example, we can compare the distance between the front and back tires to
determine the length of the wheelbase, which helps to determine the length of the
car. We can also compare the distance between the left and right tire, which
determines the width of the vehicle.
When a vehicle is traveling in a straight line, the back tires create impressions over
the front wheels, and so we only see two sets of tire tracks. When a vehicle is
turning, the front tires turn at a wider turning point than the rear tires, which means
we can see tracks from all four tires.
Topic: Soil
Humus: lots of nutrients
Soils that are rich in nutrients (and good for our tree friends) are very dark in color
Soils that have lots of sand or pebbles prevent water from collecting/pooling.
Soils that have yellow or red color are rich in iron
Porosity: how much liquid the soil will hold
Soils that allow water to pass through quickly are more porous. Soils that retain
water, causing it to run through more slowly, are less porous. [pore = hole/opening]
Particle size
Soil with small particles will feel smooth between your fingers
Soil with larger particles will feel more rough or gritty
pH level: acidity
Litmus paper can be used to test how acidic the soil sample is. The results from
these tests will only appear if the soil is highly acidic or basic (otherwise they
appear as inconclusive)
Soils become gradually more acidic over time due to two factors: rainfall and
breakdown of organic (living) matter
To help balance out the pH level in the soil, adding fertilizers that have more
alkaline ingredients can help. The most common are sodium, calcium, and
magnesium.
Content: what we find in the soil
Soils can have a large range of inorganic (non-living) or organic (living) material.
These materials can help investigators determine where a particular soil sample
came from
Topic: Animal tracks
4 types of animal track patterns:
1- Pace: large, slow moving animals shift their weight from one side of their
body to the other
2- Diagonal: quick moving animals rotate between left and right legs, making a
zig-zag pattern
3- Bound: small long-bodied animals jump their back legs forward to their front
legs, making a stitching pattern
4- Gallop: small hopping animals cross their hind legs in front of their front legs
as they leap forward
Animal track patterns can change when the animal changes speed, makes a quick
turn, or is injured.
Topic: Footwear analysis
Footwear is the most commonly found form of evidence at any crime scene.
Footprints are extremely useful pieces of evidence because each person’s footwear
is unique. Factors like where we place pressure, arch of the foot, and debris that gets
stuck on the bottom of the shoe can all help investigators figure out who committed
a crime. These are key components to Cinderella analysis as well, which look at
pressure, arch, size of toes and foot in the sole of the shoe.
Footprints in mud have depth to them, and are collected by pouring a plaster over
the print, which then hardens and is able to be taken out by the investigators. This is
called a cast.