Free Scene of the Crime by Anne Wingate

collected?
    Obviously, if a weapon is present, it must be collected and transported as gingerly as possible in hopes of preserving fingerprints. To handle a pistol or revolver, either lift it gingerly by the grips, or slide a pen or pencil, or a piece of string or wire, through the trigger guard behind—not in front of—the trigger, and lift it with that. When lifting it by the grips, carefully avoid touching the backstrap, the strip of metal separating the grips. A shoulder weapon is best lifted only after examining the weapon carefully and determining what part of this particular weapon is least likely to retain prints, because of checkering or repeated handling in exactly the same spot. ( Checkering refers to a small, checkerboard effect carved into the surface to increase grip security.)
    In real life, Be careful! Always assume that any weapon is loaded unless you personally have verified that it is not! Every year many people are killed with "unloaded" firearms! I've seen a few too many of those corpses to feel casual about the matter. In fiction, follow the needs of the plot—which may include substantial carelessness in handling and using weapons.
    In general, it is difficult to get fingerprints from firearms, because the stock (the wooden, rubber or plastic part of shoulder weapons) and the grips (the wooden, bone or plastic handles of a pistol or revolver) are either too checkered or too often handled, or both, to yield prints. Further, the metal parts are generally too well-oiled or too often handled. However, I have gotten extremely good prints from firearms, so it's always worth trying. In fiction, you can decide whether to have prints, not to have prints, or to have prints that somebody stupidly damages.
    Remember, always, that the weapon, like any other piece of evidence, should be photographed and triangulated before being moved. (This does not mean that somebody in your book can't stupidly—or deliberately—move the weapon without taking photos and measurements.)
    The weapon must be handled very carefully for several reasons.
    First, it may be still loaded, and it may have a hair trigger—that is, it may have been adjusted to discharge very easily. In fact, some shotguns will go off without anyone touching the trigger, if they are dropped or otherwise roughly handled. I worked two cases in which the victim—in one case, a twelve-year-old boy and in the other, the wife of a police sergeant—was killed with a shotgun nobody was even touching at the time. One of my cousins was seriously injured and one of my brothers narrowly escaped injury or death in two separate episodes of unintended keep-away played with a shotgun. (In both cases, the owner of the weapon was trying to get it back from a fraternal usurper.) That's something very useful in fiction, although in real life it should serve as a reminder that loaded guns should never be placed where children can get hold of them.
    Also, it is important to preserve the evidential value of the weapon, which might include fingerprints on the outside of the weapon as well as the rifling inside the barrel and the marks on the firing pin.
    It is essential to search for and collect any slugs that might be present at the scene, as when a slug missed or went through whoever it was aimed at. If it went through, the slug needs to be collected extremely carefully and put in a paper (not plastic) coin envelope, so that any moisture still on it can evaporate harmlessly. The lab might be able to locate microscopic fragments of cloth, bone or body tissue on it. If the slug has lodged in a wall or door frame, your detective should not try to dig it out. Instead, s/he should remove the entire section of wall or door frame and let the lab extricate the bullet. An ill-planned attempt to do the extrication may hopelessly damage the lands and grooves or other evidentiary markings.
    If, as often happens, the slug lodged inside the victim's body, the medical examiner after the