1

+ distance of the target

+ intermediate target

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

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

FRACTUREPOINT

FRACTUREPOINT

PLASTIC DEFORMATION

PLASTIC DEFORMATION

ELASTIC DEFORMATIONELASTIC DEFORMATION

STRAIN

STRESS

STRESS / STRAIN CURVE FOR BONE

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

Bone (skull)

Basic mecanism of Ballistic injuries to bones

8

Basic mecanism of Ballistic injuries to bones

Bone

9

ENTRANCE

Bone

Outer table

Iner table

Round to oval sharp-edge

holeLarge bevelled-

out hole (internal bevelling)

« 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

defectBullet strinking

at a very shallow angle produces a

combined entrance/exit

type effect

Fragmentation of the bullet +++

Outside

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)