Forensic imaging includes conventional radiography,
fluoroscopy and computed tomography [C.T.] which utilise ionising radiation to produce an image,
and non-ionising modalities such as Magnetic Resonance Imaging [M.R.I.].
Brogdon (1998a) noted that radiographs were submitted as forensic evidence in the courts of law within two months of Wilheim Roentgen’s discovery of x-rays in 1895,
thus recognising the connection between radiology and forensic medicine which has developed the “forensic-pathological radiological approach” to the investigation of the deceased. More than a century after the first use of x-rays in a medico-legal case,
radiography is still considered as one of the “most important supplements of modern autopsy technology” (Ludwig,
2002).
The use of radiography is unparalleled when determining and documenting the existence,
number,
localisation and identification of foreign material inside the deceased prior to autopsy (Rainio et al.,
2001).
Whole-body imaging assists in the chain of forensic documentation when the investigative team are searching for projectiles or foreign bodies,
especially in severely decomposed bodies (Thali et al.,
2003).
The radiographic images produced in such cases may be used to supplement evidential documents submitted in court.
According to Viner (Cowan and Hunt,
2008),
the most obvious use of x-rays in a potentially homicidal death is to demonstrate the location of bullet(s) within the victim’s body.
Ballistic and bony fragments can be visualised using conventional radiography in two planes,
but “small foreign bodies or those located close to the base of the skull may be masked,” and as a result,
may be ‘missed’ by the Pathologist and/or Radiologist (Karger et al.,
1998).
Even if the bullet is recovered without the aid of radiography,
ballistic fragments can easily be missed in an unaided dissection and important information such as the tract of the projectile may be lost to the ballistics expert.
Any radiographs which are taken for the purpose of a forensic investigation must be retained as permanent records and,
if required,
used as exhibits or produced in court as evidence.
Post-mortem radiology can assist in locating the projectile,
depicting the bullet track,
and may help in identifying the ammunition and weapon type used by facilitating the removal of the ballistic evidence present (Andenmatten et al.,
2008).
Many authors (DiMaio,
1998,
Messmer,
1998,
Brogdon,
1998b) note that the Forensic Pathologist can use x-rays to evaluate gunshot wounds in several ways:
- The location of the bullet –whilst this may seem straightforward from external inspection of the body,
bullets often end up in a site far distant from the entry site,
particularly if they have entered the circulatory system or have struck bone.
The natural curvature of the ribs and skull can cause bullets to change trajectory significantly.
- X-rays will also reveal whether there are bullets of a different calibre present.
This can be valuable in cases where multiple weapons are involved.
The number of bullets is also important and must be correlated with the entrance and exit wounds.
A discrepancy may lead to a search for bullets at the scene.
More than one bullet may enter through a single entrance wound,
particularly when automatic weapons are used.
- X-rays may also reveal information about the angle and direction of fire.
Small metallic fragments produced when a bullet strikes bone may lead directly to the bullet and clearly indicate the bullet’s path.
Correlating this information with the scene of the crime helps recreate the relative positions of the victim and the assailant.
While the type of weapon can frequently be determined by eyewitness reports or recovery of the weapon from the scene,
the radiographs may reveal clues as to the type of weapon.
- X-rays may be the first indication that a crime has been committed when decomposed bodies are discovered.
The normal putrefaction that occurs,
with its associated bloating of the tissues and deformity of the body,
can easily mask an entrance wound.
Bodies partially destroyed by fire or skeletonised remains should always be x-rayed to determine unsuspected foul play.
Retrieval of the metallic fragments can even help in the identification of remains if there is a gunshot wound in the past history of the deceased.
Determining the direction of travel of projectile(s) in gunshot deaths is an essential aspect of the post-mortem examination (Straathof et al.,
2000).
If post-mortem changes [e.g.
decomposition,
post-mortem insect or animal activity] have altered the entry or exit wounds,
determining the direction of fire can be very difficult for the Forensic Pathologist based on the external examination and/or the internal examination.
Traditionally,
conventional radiographs were acquired in forensic cases.
However,
this reduces a three-dimensional body to a two-dimensional image (Andenmatten et al.,
2008),
thus requiring a minimum of two radiographs from different angles,
i.e.
orthogonal projections,
to facilitate the localisation of foreign bodies within the deceased in three-dimensions (Stockman et al.,
2007) .
Two perpendicular projections are essential to determine the path of the bullet and to begin to assess potential tissue damage.
This is very time-consuming in practice,
particularly if imaging is performed outside the X-ray department,
as multiple x-rays must be performed in suboptimal conditions.
The imaging equipment available in the mortuary is often old or donated,
and the mortuary facility is usually remote from the x-ray department where processing facilities are located.
Following discussion with Professor Marie Cassidy (2010) on the use of imaging as part of the post-mortem examinations performed in Ireland,
it was realised that radiography is most commonly requested in cases of gun-related deaths.
Druid (1997) noted that 57% of the homicide victims in his study sustained more than one gunshot,
which is acknowledged to result in high morbidity and mortality (Fu et al.,
2008).