1. Toward Automatic Blood Spatter Analysis in Crime Scenes Gabriel Brostow, 13 June, 2006 Shen, Brostow, Cipolla University of Cambridge

2. Bloodstain Categories* Passive Bloodstains Projected Bloodstains –Low / medium / high velocity impact: caused by force applied to a blood source Transfer/Contact Bloodstains *International Association of Bloodstain Pattern Analysts

4. Image by Kevin Maloney

5. Point of Origin Localization

6. String Method

7. Support Software From BackTrack software by A. L. Carter, 2001 version

8. Automation Goals 1.Estimate impact angles for 1 spot 2.Estimate 2D origin of impact 3.Estimate 3D origin of impact

9. Automation Goals 1.Estimate impact angles for 1 spot 2.Estimate 2D origin of impact 3.Estimate 3D origin of impact

11. Experimental Setup

12. Results: Impact Angles

13. Primary vs. Secondary Stains Bevel & Gardner, 2001

14. Filter for Outliers

15. Automation Goals 1.Estimate impact angles for 1 spot 2.Estimate 2D origin of impact 3.Estimate 3D origin of impact

16. 2D Multi-Spot Analysis Experiment –Blunt force impact –True origin: diameter 6cm height 22cm

17. Strings in the form of vectors x y

18. Intersections

19. Convolve with Gaussian

20. Threshold on Distance

21. Image rectification Generate synthetic view Homography:

22. Image rectification

23. Automation Goals 1.Estimate impact angles for 1 spot 2.Estimate 2D origin of impact 3.Estimate 3D origin of impact

29. Height Estimation Triangulation –H = tan(  ) * distance –True height 22cm, estimated height 19cm Advanced –Unknowns –Speed, distance, air resistance and gravity

30. Height Estimation Triangulation –H = tan(  ) * distance –True height 22cm, estimated height 19cm Model in future –Speed, distance, air resistance and gravity

31. Findings Demonstrated accuracy of 1-spot analysis 2D Origin of Impact Estimation Overhead crime-scene visualization Groundwork for 3D string method automation

32. Future Work Real blood images 3D projectile trajectory modeling

34. Contact Gabriel J. Brostow gjb47@cam.ac.uk or Amy Shen ars42@cam.ac.uk University of Cambridge

36. Related work Interpretation of Bloodstain Evidence at Crime Scenes –Eckert & James, 1998 Bloodstain Pattern Analysis –Bevel & Gardner, 2001 Blood Dynamics –Wonder, 2001 The Directional Analysis of Bloodstain Patterns, Theory and Experimental Validation –A.L.Carter, 2001

37. Alternative bloodstain ellipse fitting Alternative ellipse fitting algorithm –Ellipse growth –Erosion, median filter and dilation

38. Manual vs. Automatic Current pipeline: –On-site measurements –Physical strings construction –Qualitative estimation of origin Automatic pipeline: –Image processing –Strings in the form of equations stored on computer –Quantitative estimation of origin using error functions