: Bloodstain Geometry Experiment
The purpose of this lab is to help to become familiar with the basic geometric shapes and patterns
formed by droplets of blood when they impact various target surfaces at a 90° angle. You should also
learn the about the effects that various surface textures will have on the geometry of the blood droplets as
well as how you articulate your recognition, documentation, and interpretation of the bloodstain evidence.
Finally, you will observe what blood may look like after traces of it are removed using a presumptive blood
You will document your findings, sketch the appearance of the stains, and answer some questions about
Artificial Blood Preparation
There are three variations for creating your artificial blood. Choose the method that works best for you.
1. Use 4 oz of evaporated milk, 2-3 tablespoons of tomato paste, and red food dye. Mix to the
viscosity of blood and use water to thin as necessary. This artificial blood mixture should be
freshly made; it is only good for a few days. Store in refrigerator if necessary.
2. Use 4 oz of Carnation® dry milk, red food dye, and water. Mix to the viscosity of blood.
3. Use 4 oz of white corn syrup and red food dye. Mix to the appearance of blood.
Equipment and Supplies
1. Plastic dropping pipettes
2. A few pairs of gloves
3. A face mask (as a precaution against artificial blood, since it can be messy)
4. L-Scale labels to measure and document your stains
Supplies from your local craft or discount department store:
1. A 12-inch square piece of cardboard (or something of a like texture)
2. A 12-inch square piece of plywood (or something of a like texture)
3. A 12-inch piece of ?inch thick smooth, clear piece of acrylic (or something of a like texture)
4. Paper towels
5. Tape measure
a. If you want to experiment
on an additional surface, you can also drop blood onto a floor tile,
carpet, or piece of clothing
1. Drop one drop of artificial blood straight downward onto each surface (cardboard, plywood,
acrylic, piece of paper towel) texture being tested from the height of 1 inch, 2 inches, 36 inches,
and 72 inches.
2. The test surfaces should be placed flat on the floor (not a carpeted floor) and the pipette should
be held perpendicular to the surface when the blood drops are released.
3. Draw a well-mixed quantity of the artificial blood into the pipette and wipe off any excess blood
from the outside of the pipette with another paper towel. Be careful not to include any air bubbles
with the blood.
4. Make your observations while the stains are wet and after the stains have thoroughly dried.
5. Once stains are dry and properly documented, attempt to clean up the dried blood using a slightly
6. Utilizing the alka selzer Tablets to make a presumptive test solution, you will visualize the cleaned
up blood, photographing your results and documenting your observations. Note: To make the
presumptive test solution, simply place both tablets into the spray bottle and add four ounces (4
oz.) of water. Shake thoroughly until tablets are completely dissolved. Dispose of empty
Report Observations and Documentation
1. Sketch the appearance of your blood drops at each height. Either photograph or scan your sketch
2. For each surface texture being examined, make the following observations and record your
a. Describe the texture of the surface: hard/soft; smooth/rough; porous or nonporous
b. Describe the edge characteristics of the resulting stains
c. Measure the diameter of each drop (in millimeters)
d. Describe the extent of peripheral satellite spatter
e. Discuss what effect changing the dropping height had on the resulting stains
f. Document your observations of the effect of alka selzer on the cleaned up blood; was it what
you expected? Why or why not? Did you have difficulty applying the solution?
g. If possible, experiment
with other surface textures (as previously described) and document
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