guns
Most guns work in a similar way, that is, when the trigger is pulled, it makes the firing pin hit the back of the sealed unit (bullet) and in turn, ignites the small pressure- receptive charge called a 'primer'. The primer then sets off an explosive powder in the bullet (or in the case of a shotgun, pellets), forcing it to move down the barrel, where it is expelled towards the target. The power of the explosion, a powerful chemical reaction, will give the bullet speed and force. Simple guns need to be reloaded after one or two shots, though most guns have a bullet holding area that can usually store up to five bullets or more. Semi-automatic weapons have an explosion that pushes the bullet out, as well as ejecting the used bullet cases. The weapon then automatically reloads a new bullet and pulls back the firing pin, in preparation for the next shot. In the case of automatic weapons, when the trigger is held back, the gun will continue firing until the bullet holding area is empty. The most common firearms come in the form of a revolver, a semi-automatic revolver, machine guns, hunting rifles and shotguns (loaded with pellets).
gunshot residue
Gunshot residue is found in a circular shape around the victim's bullet wound and most importantly, on the suspect's hands and clothing. Residue that is found on a suspect's hand can provide proof that the suspect handled and fired a weapon recently, but the absence of residue is not enough to prove innocence. Washing the hands can remove all traces of gunshot residue and some weapons do not expel any residue at all. Because of this, investigators will often take swabs of a suspect's clothes and face to try and find traces of residue. Other traces of residue may not be just from the bullet, but also from the oil and metal that can come in contact with the hands whilst loading a gun.
bullets
In the case of a shooting, investigators must find out how many shots were fired, where the bullets went and how each bullet got to where it is. This is done by talking to witnesses who heard the shots or saw them being fired and also looking for the used cartridges that may have been left on the ground. If the shooter dropped the weapon, it is possible to tell how many shots were fired by counting how many shots remain in the bullet holding area. Once it has been established exactly how many bullets were fired, the next step is to find all the bullets. An x-ray of the victim will show bullets lodged in the body as dark shadows. Bullets lodged in materials that are soft are especially helpful in an investigation, as the marks left behind can be useful in the identification of the weapon that fires it. If bullets are dented beyond analysis upon contact with a hard surface, it is still important to find the bullet's point of impact, as it enables investigators to trace the path from the barrel of the gun to its final resting place.
This is done using lengths of rod and pieces of string, as well as lasers, but lasers can only be sighted and photographed in specific light conditions.
This is done using lengths of rod and pieces of string, as well as lasers, but lasers can only be sighted and photographed in specific light conditions.