Wound severity

1. Wound severity • Tissue absortion of the KE is the most important and not KE potentialy possessed by the bulet • Characteristic of the missile • Velocity ++ • Mass • Ballistic shape • Design and composition • Yaw • Characteristic of the bones • Elasticity • Cohesiveness • Density • Shape + distance of the target + intermediate target

2. Extrinsic factors • Importance : duration, direction and sequence of forces • Rate of loading • Stress : internal resistance resulting of the application of an external load

3. Intrinsic factors • Resistance of bone (haversian bone, medullary bone) • Influence of ageing and pathology (osteoporosis, tumor…)

4. STRESS / STRAIN CURVE FOR BONE FRACTURE POINT PLASTIC DEFORMATION S T R E S S ELASTIC DEFORMATION STRAIN

5. Low rate of loading • Little energy absorbed : creation of linear fractures or no fracture • High rate of loading • Absorption of a high rate of energy : concentric fractrures or comminuted

6. Distant gunshot wound Abrasion Ring

7. Basic mecanism of Ballistic injuries to bones Bone (skull)

8. Basic mecanism of Ballistic injuries to bones Bone

9. ENTRANCE Outer table Iner table Round to oval sharp-edge hole Large bevelled-out hole (internal bevelling) Bone « Cone shape »

10. Entrance : exceptions • Beveling on the outer table (?) • Peterson, JFS, 1991. External bevelling AND internal bevelling • Return of gaz through the bullet? • Tempory cavity? • Rotation of the bullet? • Angle of the shot? • Shape of the bullet?

11. Entrance : exceptions • Irregular: • Yawing • Tumbling • Re-entrance

12. Exemple of exit Inside Outside - Sometimes could have blunt trauma shape in case of suture or preexisting fracture - Minimum beveling

13. Primary fracture • Secondary fracture • Tertiary fracture

14. Morphology of ballistic fracture • Primary fractures • Plug formation • Bevelling formation • « Petalling » in thin bones

15. Entrance/Exit • The magitude of entrance associated fractures (radial, concentric) are often greater than exit associated fractures.

16. Absence of radial or concentric fractures KE was totaly absorbed by primary fracture - long distance shot - low velocity bullet

17. Caliber determination by size of entrance wound ? • Usualy bigger than the caliber because of the yaw

18. Caliber determination • It may never be possible to identify the specific caliber from a simple measurement of the defect Berryman, Smith, Symes. JFS 1995

19. KEYHOLE defect Bullet strinking at a very shallow angle produces a combined entrance/exit type effect Outside Fragmentation of the bullet +++ Inside

20. Ballistic injuries to long bones

21. « Indirect fractures »? • HV bullet passes near the bone but does not contact it directly • Caused by the high pressure due to the expanding cavity

22. Need to keep bones • Evidence for Court • Understand the mechanism of fractures and the path of the projectile • Education

23. CONCLUSION • Importance of path/anthropo collaboration • Importance to compare skin and bones • Importance of X-ray (3D?) • Importance to make a meticulous reconstruction

24. CONCLUSION • Mecanism of ballistic trauma are the same on all the bones • Importance to differentiate HV trauma and LV trauma • Not realy possible to predict a bullet diameter from the orifice (often smaller than their diameter)