1. 8th Grade Forensic Science
Bloodstain Science
8th Grade Forensic Science
T. Trimpe

2. How does a blood droplet form? Click the image for an animation.
What is BPA? Bloodstain Pattern Analysis
How can an investigator use bloodstain patterns to analyze a crime scene?
Location and description of individual stains and patterns
Direction a blood droplet was traveling by calculating angles of impact
Area of origin of blood source or sources
The type of object used in attack (edged, blunt, firearm, etc.)
Minimum number of blows
The positions of the victim, suspect, and objects during events
The sequence of events
Evidence from bloodstain pattern analysis is not usually powerful enough on its own to convict someone of a crime, but it can be useful in supporting other types of evidence found at a scene.
How does a blood droplet form? Click the image for an animation.

3. Bloodstain Pattern Analysis Terms
Spatter – Bloodstains created from the application of force to the area where the blood originated.
Origin/Source – The place from where the blood spatter came from.
Angle of Impact – The angle at which a blood droplet strikes a surface.
Parent Drop – The droplet from which a satellite spatter originates.
Satellite Spatters – Small drops of blood that break of from the parent spatter when the blood droplet hits a surface.
Spines – The pointed edges of a stain that radiate out form the spatter; can help determine the direction from which the blood traveled.

4. Images from http://www.bloodspatter.com/BPATutorial.htm
Passive Bloodstains
Patterns created from the force of gravity
Drop, series of drops, flow patterns, blood pools, etc.
Projected Bloodstains
Patterns that occur when a force is applied to the source of the blood
Low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound.
Transfer or Contact Bloodstains
The pattern created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part.
Wipe pattern from an object moving through a bloodstain or swipe pattern from an object leaving a bloodstain.
Images from

5. Luminol
Used by crime scene investigators to locate traces of blood, even if it has been cleaned or removed.
A luminol solution is sprayed throughout the area under investigation.
The iron present in any blood in the area causes the chemical reaction that leads to the blue luminescence revealing the location of the blood.
Any glow detected may be documented by a long exposure photograph as the glow only lasts 30 seconds.
Luminol only shows investigators that there might be blood in an area, since it also reacts to some metals, paints, cleaning products and plant matter. A specialist can tell the difference in the chemical’s reaction to each substance, and then perform more tests to determine whether the blood is human.
Luminol also can point the way to other evidence or how events might have unfolded at a crime scene. If it is sprayed on a carpet and produces a glow, officers might peel back the rug to reveal a floorboard soaked with blood. It might also show the direction in which a criminal walked or dragged a body, or whether the victim was shot from behind or above.
One problem with luminol is that the chemical reaction can destroy other evidence in the crime scene. For this reason, investigators only use luminol after exploring a lot of other options

6. Blood Spatter – Single Drops
You will be creating sample drop patterns created by blood dropping from 4 different heights.
This can be messy! Be very careful to keep the blood on the paper and not on yourself, the table, or floor. Allow the blood to dry before you move the paper.
Obtain a piece of butcher paper (at least 1 meter long) from your teacher along with a marker, a measuring tape, safety goggles, and a bottle of blood.
Find a space for your group in the classroom and tape your paper to the floor. Write your names on the paper and label four areas for the different heights. 25 50 75
100
Names?

7. Be sure the drops don’t run together!
Hold the dropper bottle upside down so that the end of it is 25 cm from the paper. GENTLY squeeze the bottle so that ONE drop of blood is released and lands in the correct location on your paper strip. Repeat two more times at this height for a total of three trials. 25 50 75
100
Continue making drops of blood on your paper, but put the drop in a different spot on the paper and change the height each time.
Be sure the drops don’t run together!
When you are done, leave it to dry overnight. Clean up your area and put away your materials.

8. Single Drop Analysis
Now that your blood samples are dry, it’s time to do some measurements.
Use the vernier caliper to measure the diameter of each droplet. If there are spines or protrusions on the drop, don’t include those in your measurement.
Don’t measure the spines – just the diameter of the main area of the droplet.
Record your measurements in the chart on your worksheet, find the average for each height, and answer the questions.

9. Blood Spatter – Multiple Drops
You will be creating sample drop patterns created by two droplets landing the same location from 4 different heights.
This can be messy! Be very careful to keep the blood on the paper and not on yourself, the table, or floor. Allow the blood to dry before you move the paper.
Obtain a piece of butcher paper (at least 2 meters long) from your teacher along with a marker, a measuring tape, safety goggles, and a bottle of blood.
Find a space for your group in the classroom and tape your paper to the floor. Write your names on the paper and label four areas for the different heights. 25 50 75
100
Names?

10. Repeat for a total of three trials.
Hold the dropper bottle upside down so that the end of it is 25 cm from the paper. GENTLY squeeze the bottle so that ONE drop of blood is released and lands in the correct location on your paper strip.
Without moving your hand, release ONE more drop onto the first drop at that height. If you make a mistake, note that on the butcher paper and try it again.
Repeat for a total of three trials. 25 50 75
100
Continue making drops of blood on paper – three trials for each of the four heights.
When you are done, leave your paper to dry overnight. Clean up your area and put away your materials.

11. Multiple Drop Analysis
Now that your blood samples are dry, it’s time to do some measurements.
Use the vernier caliper to measure the diameter of each droplet. If there are spines or protrusions on the drop, don’t include those in this measurement.
Measure the diameter of the spread – greatest distance between the satellite
Don’t measure the spines – just the diameter of the main area of the droplet.
Record your measurements in the chart on your worksheet, find the averages, and answer the questions.

12. Blood Spatter - Motion
You will be creating sample drop patterns created by dropping blood onto a paper strip as you are walking.
This can be messy! Be very careful to keep the blood on the index cards and not on yourself, the table, or floor. Allow the blood to dry before you move the cards.
Obtain a strip of butcher paper that is 3 meters long from your teacher along with a marker, a measuring tape, and a dropper bottle of blood.
Tape your paper to the floor and label it with your names.
Walking Drops
Names

13. Hold the dropper bottle upside down so that your hand is at waist level and is over the paper.
Starting walking along the paper strip at a NORMAL RATE and GENTLY squeeze the bottle so that blood is released ONE DROP at a time. Be sure that all the drops land on your paper strip.
Walking Drops
Names
Walking Direction
Motion Drop Analysis
When you are done with each test, draw a sketch of the blood droplets on your worksheet. Answer the questions after you have finished all three tests. Clean up your area and put away your materials.

14. Blood Spatter - Angle of Impact
You will be creating sample drop patterns created by droplets landing at different angles from one drop height.
This can be messy! Be very careful to keep the blood on the paper and not on yourself, the table, or floor. Allow the blood to dry before you move the paper.
Obtain a four pieces of paper from your teacher along with a marker, a measuring tape, safety goggles, clipboard, angle guide, and a bottle of blood.
Set up the angle guide near the end of the table as shown below. Write your names on the four pieces of paper and indicate the angle for each test - 25o, 45o, 60o, and 85o.
Angle Guide
Clipboard/Paper

15. Place the first piece of paper on the clip board and set it at a 25o angle from the table. Hold the bottle of blood at a height of 50 centimeters from the top of the table.
GENTLY squeeze the bottle so that ONE drop of blood is released and lands on the paper. Repeat two more times at this angle.
Continue testing by dropping blood from a height of 50 centimeters at each of the other angles.
When you are done, leave your paper to dry overnight. Clean up your area and put away your materials.

16. Angle of Impact Analysis
Now that your blood samples are dry, it’s time to do some measurements.
Use the vernier caliper to measure the length and width of each droplet. If there are spines or protrusions on the drop, don’t include those in this measurement.
Record your measurements in the chart on your worksheet, find the averages, and answer the questions.

17. Quick Quiz
Which of the three blood droplets shown would have been created by a wound in the lower part of the leg? Explain.
If you have a blood droplet as shown at left, what does it tell you? Explain.
If you find a trail of blood with droplets that are close together, what could this mean?

18. Vernier Calipers
Vernier calipers are used for small measurements, such as determining the diameter of a blood droplet.
1st - Read the result where the “O” on the top scale lines up with a mm mark on the center scale.
2nd - Read the result where a 1/10th mark lines up EXACTLY with a mm mark.
To measure the diameter of a blood droplet, use the caliper to measure from one side to the other. Do not measure spines or protrusions.

19. Caliper Practice How did you do? Penny – Diameter = ________ mm
Triangle – Height = ________ mm
Rectangle – Length = ________ mm