BLOODSTAIN PATTERN ANALYSIS

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This session provides participants with an understanding of bloodstain pattern analysis and how the study of the size, shape, and location of bloodstains can be used to determine the physical events that gave rise to their origin.

Category

  • Exploring: Law Enforcement
  • Exploring: Science
  • S. Department of Education: Law, Public Safety, Corrections & Security
  • S. Department of Education: Government & Public Administration

Objectives

By the end of this session, participants will be able to:

 

  • List the components of human blood.
  • Identify the mechanisms by which blood spatter patterns are created.
  • Describe how the surface texture of an object affects the shape of individual bloodstains.
  • Describe the directly proportional relationship between stain diameter and dropping height.
  • Create and interpret transfer patterns.
  • Measure the length and width of bloodstains.
  • Calculate the impact angle of bloodstains.

Supplies

  • (1) computer with internet access

For each participant:

  • (1) eye dropper or pipette
  • (1) bottle of stage blood or red tempura paint
  • (1) package of white 8½-by-11-inch card stock
  • (1) meter stick
  • (1) metric ruler
  • (1) cake pan or pie plate
  • Household objects (fork, knife, sponge, hammer, wrench, screwdriver, etc.)
  • (1) scientific calculator
  • Impact Angle Determination Practice activity sheet (PDF)
  • Impact Angle Determination Practice answer key (PDF)

Advisor Note

Make sure you add time in your activities for viewing and discussing videos with the Explorers. These videos are currently not built into the session plan so you will need to choose those that best complement your activities and plans for this topic.

 

Text in italics should be read aloud to participants. As you engage your post in activities each week, please include comments, discussions, and feedback to the group relating to Character, Leadership, and Ethics. These are important attributes that make a difference in the success of youth in the workplace and in life.

Activity 1

How Bloodstain Patterns Are Created

Have participants watch as many videos as time permits from the Midwest Forensics Resource Center at www.ameslab.gov/mfrc/bpa-videos. These videos illustrate a number of different mechanisms that create bloodstain patterns.

Activity 2

Effect of Dropping Distance on Stain Diameter

Have each Explorer follow this procedure:

  • Fill an eye dropper or pipette with stage blood or red tempura paint.
  • Drop single drops of blood onto white card stock from 10 cm, 50 cm, and 1 m and allow them to dry.
  • Measure the diameter of each stain.

 

Ask: What correlation can you draw between stain diameter and dropping height?

Activity 3

Transfer Patterns

Have each Explorer follow this procedure:

  • Pour enough blood or tempura paint into a cake pan or pie plate to completely cover the bottom.
  • Choose one of the household objects, dip it into the blood or paint, and press it onto a clean piece of card stock.
  • Re-wet other parts of the same object and press onto clean white card stock. Observe how different parts of the same object can leave remarkably different patterns.
  • Repeat this for each of the selected household objects. Observe the transfer patterns.

 

Ask participants whether or not they would be able to ascertain the nature of each object if it were used in an actual criminal case.

Activity 4

Impact Angle Determination

Show the video “Blood Stain Analysis: Calculating the Area of Convergence and the Area of Origin” (National Forensic Science Technology Center): www.youtube.com/watch?v=3jFKZaSeNjg.

 

Have participants complete the Impact Angle Determination Practice activity sheet. Then review the worksheet with participants using the Impact Angle Determination Practice answer key.

Activity 5

Case Studies

Show the Forensic Files and/or Medical Detectives episodes listed under “Videos” to the Explorers and discuss how bloodstain pattern evidence helped in the investigation.

Activity 6

Speaker or Visit

If possible, make arrangements for one of the following activities in order to provide Explorers with a real-world look at the profession of forensic science.

  • Arrange for a visit to a local, county, or state crime laboratory with an emphasis on the forensic biology section.
  • Reach out to a crime laboratory or crime scene investigation unit and arrange for a bloodstain pattern analyst to talk to participants.
  • Have participants attend a trial where bloodstain pattern analysis evidence is being presented.
  • Have participants research the Sam Sheppard case. This is one of the most infamous cases in the history of bloodstain pattern analysis.

Advisor Note

Some sample questions are below. They are designed to help the participants apply what they have learned to their own interests. You are welcome to use these questions or develop your own questions that relate to your post or specific focus area.

Reflection

Focusing Questions

Analysis Questions

Generalization Questions

BLOODSTAIN PATTERN ANALYSIS ACTIVITY GUIDE
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