CASE ONE: STUDY OF EXTERNAL BALLISTIC
A patient was taken to the emergency room with gunshot wounds,
he appeared ill and sweaty,
with a bullet entrance hole in the left sacral wing,
no abdominal pain,
no hematuria.
The CT scan identified high density object in the subcutaneous inguinal region close to the right femoral artery.
The entrance hole was located in the left gluteal region,
the bullet penetrated at the posterior edge of the iliac wing and crossed the sacral sincrondrosis passing through the posterior wall of the first left sacral foramen.
The journey continued with sacral fracture and leakage from the body of S2.
In peritoneal space at the back of the internal iliac neurovascular bundle,
was observed hyperdensity involvement without traumatic changes of opacification of the right internal iliac artery.
The density of the subcutaneous tissue of the inguinal region was increased type blood,
as a landmarks of the projectile.
CMPR (Curved Multi Planar Reformation) reconstruction algoritm,
showed the passage of the projectile through the structures and his journey (Fig.
1).
The images were then uploaded to the software (External Beam Planning 6.5 "Varian Medical System) and 3D reconstructions demonstrated the path of the projectile through the bony structures and soft tissues (Fig.
2)
In this case,
the evaluation of transitions and the subsequent reconstruction of the direction identified the trajectory of the projectile.
After the reconstruction it was possible to identify the angle of penetration of the projectile in the skin.
In this case,
we could hypothesize that the projectile was fired from left to right,
top to bottom with an angle of penetration of 29° over the X axis (an imaginary line parallel to the ground) (Fig.3)
In this case the internal ballistics appeared substantially linear,
the projectile was decelerated throughout his initial velocity from the bony structures and the crossed muscle,
and then it had no sufficient kinetic energy to pierce the skin of the opposite side,
so it was stuck in the inguinal canal.
The trajectory of the bullet allowed us to conclude that the shot was fired from behind,
from above downwards pointing the patient from the waist down,
and was shot by an assailant located to the left,
approximately 80-90cm from the victim .
The last distance was calculated by an approximate simple trigonometric calculation in which a cathetus is equal to the other cathetus multiplied the cotangent of the adjacent angle,
(Fig.4) where the cathetus missing is the distance and the cathetus inserted in the formula corresponds to the estimated distance of the gun to the point of retention (in this case the length in an average man from the shoulder to the groin).
The distance between the groin and the middle third of the humeral head of the patient “AB” is about61.8 cm,
this estimate was calculated by a MIP reconstruction in the sagittal plane (Volume viewer2,
GE) (Fig.4a).
Assuming that the patient and the aggressor had a medium and equal height,
it is possible to estimate,
on a rather approximate the cathetus C1.
The cotangent of the angle of the shot is 1.81,
which is the cotangent of 29°.
The result of that trigonometry is 111.85cm.
At this distance we have to subtract the distance “CD” (the distance of the bullet from the opposide side of the body),
that was calculated in axial view,
from the projectile to the opposite cutaneous margin,
that was estimated23,6 cm(Fig.5b).
We can therefore conclude with a summary that the distance was about 88cm.
CASE TWO: STUDY OF TERMINAL BALLISTIC
Unknown male patient was taken to the emergency room in a deep coma (GCS 3),
he was spontaneously breathing (28 breaths / min),
no brain stem reflexes were present,
with a severe facial trauma from a possible accidental fall and copious nose and throat bleeding.
Tracheal intubation was carried and the patient was put in invasive external respiration.
CT scan examination revealed in the left occipital lobe the presence of an high density material to report as a projectile.
The entrance hole was identified at the hard palate,
with multifragmentary fractures involving the posterior wall of the sphenoid sinus and the left frontal and ethmoidal sinus.
The presence of a subdural hematoma in the left frontal-parieto-temporo-occipital lobes with a maximum thickness of about 17mm,
caused compressive effects on the surrounding brain structures,
and a midline shift to the right of around 11mm.
The CT images were included in the dedicated software,
which revealed the trajectory of the projectile and his steps.
The mark of the holes allowed to highlight ultimately the terminal ballistics of the bullet in the skull,
reconstructing the movement in a more accurate mood.
The shot,
had been fired at the level of the hard palate in the left paramedian zone,
then was decelerated by the bony structures of the hard palate and the sphenoid,
losing the kinetic energy needed to break through the skull,
was then deflected by the structure of the frontal bone in the fossa of the superior sagittal sinus,
it lost more kinetic energy,
bouncing in the parietal bone and finally crashed against the left external occipital protuberance and having lost all its kinetic energy found its final location at the ipsilateral occipital brain parenchyma.
After the post-processing,
and using a software for imaging manipulation (GIMP 2.6.11,GNU Image Manipulation Program) to connect the displayed points,
it was clearly evaluable the internal trajectory of the bullets and it was possible to define that the shot was fired with an inclination from right to left,
from bottom to top (Fig.7),
which allowed to conclude that the patient had the gun in his right hand,
and assuming that the patient was a right handed,
we could exclude the involvement of third parties in the event.