From: gmk@falstaff.MAE.CWRU.EDU (Geoff Kotzar)
Subject: Re: (DEFENSE) Fingerprints on cases (was Re: home protection concerns)
In article <C1nrpr.BC7@constellation.ecn.uoknor.edu> firstname.lastname@example.org (James P. Callison) writes:
#By chance, have any of you looked at the cases an autoloader deposits after
#firing? If you have, you will notice something--scratch marks. All over the
#thing. Since the case is expanded by the expanding gases, it gets scratched
#by the chamber. Now think of how you load your magazine.
#You see? Most of the print you left was erased by the extraction process;
This statement is not true. Vincent DiMaio in his book "Gunshot Wounds"
has a section on forensics. He makes a point of noting that very frequently
there are no useful prints to be found on the firearm itself. This is because
the gun shifts during recoil smudging the prints and because there are very
few surfaces large enough for a print to be deposited on to begin with. He
does go on to state explicitly that spent cases must be handled carefully
because they often are the only source of useful prints. In a separate
article I found a reference to removing prints from the dropped magazine.
Plese note that these articles were originally intended for forensic pathol-
ogists and forecsic ballisticians. Perhaps the phrase I should have used was
"lifting the prints" instead of "removing the prints".
#I'll wager that you won't find nearly enough of a print to make the six-point
#match. Any prints you find which are identifiable will necessarily have
#been made _after_ the cartridge was fired. (And absolutely forget getting
#prints off the bullet itself; there won't be any.)
This particular book has a bunch of interesting info on forensics even though
that is not its main focus. One of the most nteresting is that there are three
methods of determining if an inidividual handled a recently discharged firearm.
Frequently .357 mags do not deposit enough primer residue on the shooters hands
to allow a positive result from two of the three methods. The third method is
very positive since it does not rely on quantity of deposited lead, barium and
antimony but rather on the shape of the deposits which for primer residue are
very unique. This latter method is scanning electron microscopy. Of the first
two, one is called flame atomic absorption spectrum (FAAS) and the other name
escapes me at the moment. The book is at home.