From this thread here, I decided to make a new one...
http://www.thefiringline.com/forums/showthread.php?t=255521&page=2
@ easyG
As a side note I would be interested to know what your technique was for measuring the size of those rounds based on the radiographs.
I found that it is impossible with retrospective analysis and it is prone to inaccuracy even with prospective techniques. My best shot with combined plain film and CT has lead me to the conclusion that you cannot tell the difference between calibres with a small diameter difference between them (such as .357 and 9mm) even in an immobile 'subject.'
With a live patient results will be worse. The best you can do is establish what the maximum size of the projectile can be. There are too many variables to take care of retrospectively, from bullet-to-detector distance to geometric unsharpness. It makes it very difficult to work out the degree to which the shadow seen on the radiograph has been magnified or otherwise distorted.
There are some instances where a calibre determination can be made radiologically, but in those cases the investigators have narrowed the possibilities down to two or three diameters before they embark on a radiological investigation.
For example prospective imaging was employed to determine the size of a shotgun pellet in a man's eye, in a case where there were only two possible shooters and three possible pellet sizes. This was an accident where a third man was hit in the eye and they needed to find the liable shooter.
But that technique can't be employed in cases where you don't have any information outside of the patient and you need to X-ray him and make a guess on calibre.
http://www.astm.org/cgi-bin/SoftCart.exe/JOURNALS/FORENSIC/PAGES/3115.htm?E+mystore
http://www.thefiringline.com/forums/showthread.php?t=255521&page=2
@ easyG
As a side note I would be interested to know what your technique was for measuring the size of those rounds based on the radiographs.
I found that it is impossible with retrospective analysis and it is prone to inaccuracy even with prospective techniques. My best shot with combined plain film and CT has lead me to the conclusion that you cannot tell the difference between calibres with a small diameter difference between them (such as .357 and 9mm) even in an immobile 'subject.'
With a live patient results will be worse. The best you can do is establish what the maximum size of the projectile can be. There are too many variables to take care of retrospectively, from bullet-to-detector distance to geometric unsharpness. It makes it very difficult to work out the degree to which the shadow seen on the radiograph has been magnified or otherwise distorted.
There are some instances where a calibre determination can be made radiologically, but in those cases the investigators have narrowed the possibilities down to two or three diameters before they embark on a radiological investigation.
For example prospective imaging was employed to determine the size of a shotgun pellet in a man's eye, in a case where there were only two possible shooters and three possible pellet sizes. This was an accident where a third man was hit in the eye and they needed to find the liable shooter.
But that technique can't be employed in cases where you don't have any information outside of the patient and you need to X-ray him and make a guess on calibre.
http://www.astm.org/cgi-bin/SoftCart.exe/JOURNALS/FORENSIC/PAGES/3115.htm?E+mystore