BLOOD SPATTER ANALYSIS
Part A: Relationship Between Shape and Impact Angle for Bloodstains
Procedure:
1. Assemble the Impact angle apparatus
Tape one end of the cardboard to the table by making a hinge out of the tape. The cardboard
should be right at the edge of the table. Hold the protractor to the edge of the clipboard so that
the protractor is perpendicular to the table top and aligned so that the center of the protractor is at
the edge of the hinged-end of the clipboard. See Figure 1 below.
2. Label a piece of scrap paper 100. Attach the scrap paper to the cardboard. Set the angle of the board,
using the protractor, so that the board will have the correct angle of 100.
To obtain the desired impact angle, set the impact angle cardboard to a protractor setting of 900
minus the desired impact angle. For example, to obtain a 600 impact angel, set the board at a
protractor setting of 300. See figure 1 above.
3. Place the dropper bottle of blood approximately 30 cm above the impact angle board.
4. Allow a drop of blood to fall onto the target.
5. Allow the drop to dry and then store the card in some safe place.
6. Record the data on the chart: a sketch, the widths and lengths of the stain, and the calculated impact
angle.
7. Repeat steps 2-6 for the remaining impact angles.
DATA TABLE:
Impact angle
100
200
300
400
500
600
700
800
900
Sketch
Stain width
Stain length
Calculated angle
Part B: Vertical Drip Pattern Recognition
Procedure:
1. Drop a single drop of blood from dropping distances of 15cm, 30cm, 60cm, 100cm onto each of the
following surfaces: newspaper, plastic bag, carpet, linoleum, and fabric.
2. Deposit the drops from all 4 distances on each surface before cleaning and/or destroying the surfaces.
3. Record the diameters and sketches of the resulting bloodstains on the data sheet.
NEWSPAPER
Height of
Blood Drop
Diameter of
blood drop
PLASTIC BAG
Sketch of
blood drop
Height of
Blood Drop
15 cm
15 cm
30 cm
30 cm
60 cm
60 cm
100 cm
100 cm
CARPET
Height of
Blood Drop
Diameter of
blood drop
Diameter of
blood drop
Sketch of
blood drop
LINOLEUM
Sketch of
blood drop
Height of
Blood Drop
15 cm
15 cm
30 cm
30 cm
60 cm
60 cm
100 cm
100 cm
Diameter of
blood drop
Sketch of
blood drop
Diameter of
blood drop
Sketch of
blood drop
FABRIC
Height of
Blood Drop
Diameter of
blood drop
Sketch of
blood drop
Height of
Blood Drop
15 cm
60 cm
30 cm
100 cm
Part C: Multiple Blood Drop Pattern Recognition
1. Drip a single drop of blood onto a target surface from a height of 30cm. Record your observations onto
the data table
2. Do not move your hand from the 30cm position. Drop a second drop of blood onto the first. Record
your observations onto the data table.
3. Drop a third drop from the 30cm position so that the drop lands on the stain from the first two drops.
Record your observations
4. Drop a fourth drop from the 30cm position so that the drop lands on the stain from the first three drops.
Record your observations
Blood Drops
One
Two
Three
Four
Obsevations: written description and pictoral
Part D: Impact Force and Blood Stain Patterns: Size of the Blood Drop
Part 1: Medium Velocity Impact Spatter Procedure
1. Tape the target surface (poster paper or computer paper) to a vertical wall or board.
2. Position your hand horizontally approximately 20-30 cm from the target surface with the palm side
down, and the fingers parallel to the surface. Place a small pool of blood on the top of your hand. See
figure 4.
3. Using the fingers of your other hand, slap the hand with the pool of blood pushing your fingers forward
in a perpendicular orientation to the target surface. See figure 4 again.
4. Carefully remove the target surface with the bloodstain, label it as “Medium Velocity Impact Spatter, 90
degree angle”, and allow it to dry.
5. Repeat steps 1-2 above. This time slap the bloodied hand with your fingers of the other hand and pus
the fingers at an angle OTHER THAN 90 DEGREES.
6. Repeat step 4, but label the stain as “Medium Velocity Impact Spatter, non-90 degree angle.
7. When the stains are dry, tape a small section of your stain patterns in the appropriate boxes provided in
the data table below. Circle a good sample stain on each.
Part 2: High Velocity Impact Spatter
1. Tape the target surface (poster paper or computer paper) to a vertical wall or board.
2. Using a hard bristle toothbrush, cover the top tips of the brush with blood.
3. Aim the brush directly at the target surface (perpendicular to the surface) and rub your finger across the
tips from front to back, so that the blood sprays onto the surface. The pattern will be very light and th
blood drops will be small.
4. Carefully remove the target surface with the bloodstain, label it as “High Velocity Impact Spatter, 90
degree angle”, and allow it to dry
5. Repeat the process in steps 1-3 above, but this time orient your brush at and angle (other than 90) to the
target surface.
6. Carefully remove the target surface with the bloodstain, label it as “High Velocity Impact Spatter, non90 degree angle”, and allow it to dry
7. Tape a small section of your stain patterns in the appropriate boxes below. Circle a good sample stain
on each.
Medium Velocity Impact Spatter 90 degrees
Medium Velocity Impact Spatter non-90 degrees
High Velocity Impact Spatter 90 degrees
High Velocity Impact Spatter non-90 degrees
Part E: Common Blood Stain Patterns
Part 1: Walking Drip Pattern
1. Tape a 6 foot long sheet of paper to the floor.
2. Squeeze the dropper bottle of blood so that drops begin to fall. Begin walking at a normal rate while
drops continue to fall. Try to keep the drops on the paper.
3. Describe and draw the pattern of the droplets on the floor below
Part 2: Cast-off Spatter
1. Place several pieces of paper on a flat surface such as a wall and secure them with tape.
2. Place about 1mL of blood one the edge of a plastic knife.
3. Use a horizontal slashing motion in the direction of the surface, deposit blood on the target surface. Go
back and forth several times.
4. Describe and draw the pattern of the droplets on the surface below
Part F: Direction of Travel and Area of Convergence
1. Lay newspapers smoothly on the floor and tape it in place. It must cover at least 10 linoleum tiles in
length and 5 in width.
2. Dip a toothbrush into a container of blood.
3. Grip the toothbrush in your hand such that when your arm hangs freely at your side, the bristle end of
the brush is down and pointed backwards.
4. Quickly and firmly flip your forearm up and back (down) twice.
5. Standing in the same spot, rotate your body to the left a couple of degrees and again quickly and firmly
flip your arm up and down twice.
6. Rotate and repeat again. At this point, a nice blood spatter should have formed on the paper.
7. Select 5-7 of the best defined tear-dropped droplets (those that show the direction of travel) on the paper.
8. Draw an extended longitudinal axis through the head and tail of each droplet using a meter stick. The
point of the linear intersection is the area of Convergence. See diagram below.
9. Use the digital camera to photograph your finished product. Copy and paste it below.
10. Each person in the group is to then choose one blood drop. Cut it out and find its angle of impact.
Picture of blood spatter and area of convergence:
Blood droplet and angle of impact calculations:
Part G: The Point of Origin.
1. Determine the width, length, and impact angle (!) for the bloodstain marked A-F. Fill in the
information in the chart below.
Bloodstain
Width (mm)
Length (mm)
Impact Angle
A
B
C
D
E
F
2. Determine the area of convergence. Stretch the string through the long axis of each the chosen blood
stains (A-F) and locate the area of convergence (where the string segments cross each other)
3. Place a ring stand onto the area of convergence. Do NOT move the ring stand or the blood stains once
the ring stand is place at the area of convergence.
4. Using the string and a protractor, raise the string to the calculated angle of impact and attach it to the
ring stand for each blood stain. Where all of the strings intersect is the point of origin.
5. Measure the height the incident occurred at in cm (the height of the point of origin). Write the
results on the line ________________________
6. Use the digital camera to photograph your finished product.
Paste the picture below.
!"#!$%&'"#()%*&+'"#&(
General blood spatter questions
1. In general, what 4 things can be determined by blood stain evidence?
2. In what other ways can blood be used as forensic evidence?
3. Observe the following blood droplets and patterns. What type of event could have occurred to produce
these patterns? Explain your answer.
a.
b.
Part A: Relationship Between Shape and Impact Angle for Bloodstains
1. What is the relationship between the elongation of a blood spot and its angle of impact?
2. What could have caused a difference between the angle given on the measurement instrument and the
actual calculation of the angle?
3. In your own words, describe how you will be able to look at a blood stain and tell the angle from which
it hit the surface.
Part B: Vertical Drip Pattern Recognition
1. What affect did increasing the distance from which the blood drop fell have on the resulting diameter of
the bloodstain?
2. How does the surface texture affect the resulting bloodstain diameter?
3. Did the degree of satellite spattering increase or decrease as your dropping height increased? Give a
possible explanation for your results.
4. Why is it important to know how blood patterns differ on different surfaces?
5. What differences did you see in blood that was dropped onto smooth and rough surfaces?
6. Create a graph that illustrates the Drop Height vs. Diameter for the blood drops on each surface (you
will have 5 separate graph lines). Name the x-axis “dropping distance (cm)” and the y-axis “bloodstain
diameter (cm).” Connect the dots. Attach the graph to this lab.
7. Use your graph to approximate the diameter of a bloodstain that fell from a height of 45 cm on each type
of surface
a. Newspaper =
b. Carpet =
c. Plastic bag =
d. Linoleum =
e. Fabric =
8. Give the following diameters of blood drops, from what height (approximately) did they fall?
a. 0.8 cm =
b. 1.4 cm =
c. 1.8 cm =
Part C: Multiple Blood Drop Pattern Recognition
1. Did the amount of blood released from the dropper have any effect on the shape of the stain? Explain
your answer.
Part D: Impact Force and Blood Stain Patterns: Size of the Blood Drop
1. What was the main difference between medium and high velocity impact spatter?
2. What affect did changing the angle of impact have on medium and high velocity impact spatter?
Part E: Common Blood Stain Patterns
1. Draw and describe the approximate size and shape of a droplet of blood that has:
a. Fallen straight down from a height of four feet
b. Fallen from a running person from a height of four feet.
Part F: Direction of Travel and Area of Convergence
1. How can you determine the direction that the blood was traveling?
2. Describe how you can determine the convergence of blood spatter.
Part G: Origin of Spatter
Stain 9
Stain 7
Stain 8
Stain 6
Stain 2
Stain 4
Stain 3
Stain 1
Stian 5
1. Examine the crime scene diagram above and determine the position of each man at the time of the
shootings by completing the lines of convergence. Label each position either Man 1 or Man 2.
2. Both men were shot and died. Which man do you believe could have died instantly? Support your
answer with evidence from the crime scene.
3. Data Table 1 contains some of the measurements for the bloodstains found at each position. Complete
the table by filling in the blanks.
Stain
#
Length
of Stain
(mm)
Width of
Stain
(mm)
1
18.1
9.6
4.0
2
18.6
9.0
4.4
3
17.8
13.2
2.2
4
18.9
12.8
2.8
5
19.2
13.2
2.5
6
9.0
4.5
10.1
7
10.6
5.1
10.3
8
8.4
3.9
10.4
9
8.1
3.6
10.3
Width/Length
Angle of
Impact
Distance of
bloodstain
from area of
convergence
(feet)
Tangent value
of the angle of
impact
Height of the
impact
H= tangent X distance
4. Using the information you completed in data table one, which man you think was shot in the head and
which man was shot in the stomach. Explain your conclusions.
Part H: Putting It All Together
Case Study #1
Late one night a 911 emergency operator received a frantic phone call from a female name Susan Wordsworth
stating that “her boyfriend had fallen down the stairs and hurt himself.” When paramedics arrived they found a
45 year-old advertising executive name Phil Bordman lying unconscious at the bottom of his stairs, while the
following bloodstain patterns were found on a wall near the top of the stairs.
Phil’s sister reported talking to him on the phone around 4:00 pm that day. He told her that he was going to end
his relationship with Susan that evening. When Susan was questioned aout this, she explained that she and Phil
had spent an uneventful evening watching TV and mad no mention of a breakup. She also said that Phil was
going downstairs to get something to eat when she heard him yell, followed a few seconds later by a loud thud.
She thought that he must have accidentally slipped and hit his head on the railing as he fell down the stairs.
When police check the stair railing for blood they find nothing.
Using the story and diagram and your knowledge of blood spatter evidence, do you think Phil’s death was an
accident? Explain why or why not.