+ distance of the 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 + distance of the target + intermediate target

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

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

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

Low rate of loading High 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

Distant gunshot wound Abrasion Ring

Basic mecanism of Ballistic injuries to bones Bone (skull)

Basic mecanism of Ballistic injuries to bones

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

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?

Entrance : exceptions Irregular: Yawing Tumbling Re-entrance

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

Primary fracture Secondary fracture Tertiary fracture

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

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

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

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

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

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

Ballistic injuries to long bones

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

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

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

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)