1. Blood Spatter Pattern Analysis
Integrated Math
Criminal Justice I
Mrs. Watt

5. Spatter Patterns

6. Blood Spatter Evidence Activity Drop Patterns from a Vertical Impact
Blood spatter evidence plays a key part in forensic analysis. We are going to see if there is a relationship between the diameter of the droplet and the vertical height from which is was dropped.
Any Predictions ?????

7. Activity - Directions
Students will drop 1 blood droplet from each of the following heights (perpendicular to the floor) onto index cards: 15 cm, 30cm, 45cm, 60cm, 75cm, 100cm and 150cm. This is at least a 2-3 person job. Work together.
Students will use a Ward’s Vernier caliper to measure droplet diameter in mm.

8. Directions continued….
Data collection will be done in small groups.
Each Team will receive a copy of a data table to record the diameter of each blood droplet. Each Group must complete a data table.
Measure the diameter NOT including the spines. See diagram on next slide.

10. Directions continued…..
Measure the diameter (in mm) of the drop for each of the different distances dropped. This is at least a 2-3 person job. Work together.
Fill in the data table on your worksheet.

11. Graphing the Results - Sample

12. Blood spatter evidence recovered.
Determine the diameter of the blood spatter evidence collected from the scene and determine the height from which the blood drop fell. (This may reflect the height of the wound and help determine the site.)

13. BLOOD SPATTER LAB Relationship Between Blood Drop Shape and Impact Angle
Materials Needed per Group
Simulated Drip and Projected Blood
5 X 8 notecards
15 cm and 30 cm rulers
Impact angle apparatus
Tape

14. Assembling the Impact angle apparatus
Tape one end of the clipboard to a table by making a hinge out of tape. The clipboard should be right at the edge of the table. Hold the protector 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 the figure in the next slide.

15. Impact Angle Set Up
Protractor
Clipboard
60°
30º
Table
Tape

16. Select an Impact Angle to Study
Your data table (on your worksheet) includes angles from 10° to 90°.
Once you have selected an impact angle, indicate the angle on the card and then attach the card to the board.

17. Clipboard
Clip
Notecard
Clipboard

18. Directions continued….
Set the angle of the board using the protractor so that the board will have the correct impact angle. You will need to work together as a team to achieve this.
To obtain the desired impact angle, set the impact angle board to a protractor setting of 90° minus the desired impact angle. (For example, to obtain a 60° impact angle, set the board at a protractor setting of 30°).

19. Directions continued….
Using the Simulated Drip and Projected Blood, place the dropper at approximately 30 cm above the impact angle board.
Allow two to three drops to fall sequentially onto the card. Move your hand so that the drops don’t overlap. Using multiple drops will allow you to see the variation that single drops may display when striking the surface. Leave the card in position for 2-3 minutes before carefully removing it.

20. Directions continued…..
Allow the drops to dry thoroughly on the cards and then store in a safe place.
When we return, we will record your observations including a sketch in the data table provided. We will also include the diameter and length of the circle or ellipse created.

21. Calculations with Blood Spatters
To find the point of hemorrhage (POH), you must first determine the two-dimensional point of convergence (POC). The POC is the intersection where lines drawn through the center of the individual drops meet (at the X-Y axis intersection).
This is determined by drawing lines or placing strings through the long axis of individual spatters.

22. Point of Convergence (POC)

23. Angle of Impact (AOI)
The AOI for representative bloodstains helps to generate the 3rd dimension
(z-axis) in a crime scene.
This shows how high up off the ground the impact occurred.

24. To Determine the Angle of Impact (AOI):
Where opposite = width (W) and hypotenuse = length (L)
Angle of impact = ArcSIN of W/L ratio
First calculate ratio (W/L)
You should remember that you can use SIN-1(2nd key) to get degree of AOI.

25. To complete our Blood Spatter Project . . .
In a small group, look over the information gathered from the Blood Spatter Lab activity.
Complete the lab analysis worksheet provided.

26. Citations www.historychannel.co.uk
The Forensic Examiner – Summer 2005: Article by Louis L. Akin, LPI
Bloodstain Pattern Analysis tutorial by J. Slemko forensic consulting

27. Citations, continued. Ward’s bloodspatter analysis lab kitBloodstain
Pattern Analysis tutorial by J. Slemko forensic consulting