some links regarding GSR and the forensics of it.
http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNGSR.html
GSR could be present on the deceased and on the assailants clothing and may be identifiable even if the body is partly or totally decomposed.
Clothing is a good medium for the preservation of GSR and it will remain there even if long periods of time have elapsed between the moment of shooting and the time of collection (Schwoeble and Exline, 2000) .
[BBM I found this hopeful. I hope LE got the boys' clothes. Even if they had changed them, I doubt they had been laundered, so it is my hope they were not destroyed or dumped somewhere. If they were taken in one of the searches executed, good odds in there still being evidence on them]
http://forensicarchaeology.org/archives/315
IV. Gunshot Residue Deposition on the Firer
Handguns
During discharge, revolvers and pistols leak residues from parts of the gun near the firing hand. There are three sources of deposit:
(1) Leakage from gaps in the firing mechanism. Revolvers have a small gap between the cylinder and the rear end of the barrel. Some gunshot residues are leaked from this gap and deposited on the firer during discharge.
(2) Emission at ejection of the cartridge case. In semiautomatic pistols, as the bullet moves out of the barrel, another mechanism opens the breech and ejects the spent cartridge case. During this process, some gunshot residues are released and deposited on the firer.
(3) Blowback from the muzzle cloud. The major portion of gunshot residues are emitted from the muzzle of the weapon and some of these residues may flash back and be deposited on the firer.
Krishnan (49) concluded that pistols and revolvers deposit more residues on the firing hand compared to the non-firing hand, but this may not always be the case because the concentration and/or location of the residue depends on the shooting stance and grip used. Generally for this type of weapon, the larger the caliber, the larger is the likely amount of gunshot residue to be deposited on the hand. The gunshot residues on the firing hand are mostly deposited in the web area (34). This is the V-shaped part of the hand between the thumb and forefinger facing upward when the handgun is fired and is the area in closest contact to gases escaping along the side or back of the gun during discharge. Residues may also be deposited on the forearm or sleeves and the front of the chest from both revolvers and pistols (26,34). Other skin surfaces such as face and throat have also been reported to be useful sources of gunshot residues (35). Mere handling or loading of a firearm, as opposed to firing, is inferred from the detection of gunshot residues on the palm or inside of the hand (34).
[very comprehensive link]
http://www.wavesignal.com/forensics/GSR.html
