Scene of the Crime (9 page)

The Examiner's Role

The arrangement of lands and grooves and the twist of the spiraling vary according to the caliber, make and model of a firearm. So, faced with an undamaged or lightly damaged slug fired from an unknown weapon, the firearms examiner can generally say, with a very high degree of certainty, what make, model and caliber of gun fired it. A severely damaged slug, of course, may make such identification impossible. The slug can be severely damaged in any one or more of several ways. First, it is hot as it leaves the gun barrel. As it flies through the air simultaneously piercing the air and spinning, it continues to be heated by the friction of the air molecules. A soft lead bullet, striking anything hard, will tend to
splat!
and distort quite a lot; a copper- or steel-jacketed bullet may distort less from the splat effect but may shatter if it hits bone or metal. On the other hand, even a soft lead bullet that passes through only soft tissue probably will have very little distortion.

A shotgun differs in this regard, in that, generally, the shot is not marked by the barrel. Therefore, it is not generally possible to say what load of shot came from what shotgun.

When the gun is discharged, the
firing pin
hits the back of the shell either on the center or on the rim (depending on whether the weapon is center-fire or rim-fire), marking it in a way that, like the marks of the rifling, is distinctive. Therefore it is almost always possible to say what rifle, revolver, pistol or shotgun fired what cartridge or shell.

What About Caliber and Gauge?

You've heard firearms described as .45-caliber, 12-gauge. If you're a hunter or if you've been in the military, you probably know what those terms mean. Otherwise, you don't. So here goes.

Gauge,
which is used to measure only shotguns, has to do with the weight, in fractions of a pound, of what the shotgun would fire if it were firing solid ball ammunition instead of pellets. Thus, a 12-gauge shotgun would fire a solid ball of lead weighing 1/12 of a pound; a 10-gauge shotgun would fire a solid ball of lead weighing 1/10 of a pound. (I'd hesitate even to write about home-loading a shotgun shell this way. I'd be afraid somebody would try to do what I said and wind up blowing up the barrel, with probably fatal results.) Although theoretically this round ball of lead would exactly fit the barrel, I suspect the fit may be rather tight. The shotgun, remember, is not rifled. (It is possible to purchase rifled slugs for shotguns, but they are specially made.)

Shotgun shells are changing:
Shotguns are customarily used for shooting wildfowl. There have been repeated incidents of ducks and geese dying by flocks from lead poisoning when lake levels dropped and the birds, instinctively seeking the small gravel they customarily have in their crops to allow them to digest their food, consumed lead shot left on the bottom of the lake. As a result, more and more shotgun shells are being made with safer steel shot instead of lead shot. Shotgun aficionados argue at great length as to whether the steel shot is better or worse than lead shot; what is certain is that it is lighter, and therefore steel shot needs to be about two shot sizes larger to have about the same shot pattern as lead shot. University of Utah student Joel Grose researched this situation in depth for a paper and reported that an ounce of number-six steel shot will have a considerably tighter shot pattern (that is, more pellets concentrated in a smaller area) than an ounce of number-six lead shot; in order to get the same shot pattern, number-four or even number-three steel shot would have to be substituted. (The number here pertains to a formula that calculates the number of pellets per ounce. For more detailed information, you might prefer to talk with the owner of a gun shop, as s/he can answer specific questions.)

Grose further pointed out that a shotgun, because of its smooth bore, cannot be at all accurate at over about fifty or fifty-five yards. These items of information might be useful in writing, particularly if your character is firing a shotgun using an old shell loaded with lead shot and then a new shell loaded with steel shot.

What does
caliber
mean?
Caliber,
which is used to describe weapons other than shotguns, has to do with the nominal diameter of the barrel (hence of the ammunition) expressed in hundredths of an inch; in real life, there are some discrepancies, but this is another of those areas I would not attempt to discuss in fiction without first talking with a gunsmith. Thus, a .38 revolver has a barrel .38-inch in diameter. A .30-caliber rifle fires bullets .30-inch in diameter.
Magnum
used in a description of a firearm refers not to the caliber but to the firepower of the propellant used; however, normally a magnum firearm is a slightly different caliber from the closest caliber of regular firearm—thus, you have .357 magnums which can fire .38 ammunition, but don't try to fire .357 magnum ammunition in a .38 revolver; it will fit the chamber and cylinder, but the firing mechanism and the barrel aren't meant to withstand a magnum load. However, .45-caliber ammunition cannot be used in a .44 magnum firearm at all, nor, of course, can .44 magnum ammo be used in a .45-caliber firearm. In general, it is
extremely dangerous
to attempt to fire anything in any firearm other than the ammunition designed to fit it. Even though in some cases ammunition may appear to fit, it may actually damage the barrel and/or firing chamber irreparably or even cause an explosion.

Some calibers of guns and ammunition, such as the 9mm, are

measured in millimeters rather than in inches. This measurement format, however, remains relatively uncommon in American-made civilian firearms, although it is frequently encountered in European-designed weaponry and in military firearms.

Sometimes, ammunition and the weapons that use that ammunition are described by a name that refers both to the caliber and to the year that specific type of ammunition was first used. .30-30 ammunition was first used in 1930; .30-06 (in speech, this is called
thirty-ought-six)
was first used in 1906. Where weapons seem to be the same caliber but the ammunition is not interchangeable, the difference usually has to do with such things as the overall length of the cartridge and/or the explosive force of the charge, as in the case of the .22 short, the .22 long, and the .22 long rifle ammunition, which in most but not all guns can be used interchangeably.

How can you tell whether any given ammo can be used in any given firearm? If the weapon is yours and you bought it new, the manufacturer's instructions will tell you. Otherwise, ask someone knowledgeable. By the time you're into that type of question, you've reached the point where you need a good reference book exclusively about firearms, or even better, a good gunsmith who will patiently answer questions.

The number of lands and grooves (which of course is identical, as each two lands are separated by a groove and each two grooves are separated by a land) and the direction of twist cannot possibly be addressed in this book; firearms examiners have immense reference books containing this information. Short tables for hundreds of the more common firearms appear in
American Ammunition and Ballistics
by Edward Matunas, which is listed in the bibliography. If it is not in your library, you can obtain a copy of it through interlibrary loan.

More Information Sources

Obviously, this is only the bare beginning of an outline about weapons. If you intend to get at all technical in your fiction, you would be well advised to buy several good reference books—at least one current one such as
The Shooter's Bible,
which appears annually, and at least one on historical firearms. Michael Newton's
Armed and Dangerous: A Writer's Guide to Weapons,
published by Writer's Di-

gest Books, is especially useful, as it is designed for the writer rather than for the police officer or forensics technician.

Firearms at the Scene

What firearms evidence should be collected at the scene of the crime? What can be determined from what is 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 autopsy should, depending on the jurisdiction, turn the slug over to the investigating officer or directly over to the lab.

What Would Happen in Your Jurisdiction?

How do you know what would happen in your jurisdiction?

Ask the crime-scene technician. You may need to ask a public relations officer to introduce you to the crime-scene technician, but chances are the public relations officer himself or herself does not possess the crime-scene information you need.

While you're about it, find out whether your jurisdiction has a coroner only, a medical examiner only, or a coroner and a medical examiner. If it has a coroner, find out what his/her qualifications are. Many coroners are no more than funeral directors. You can do a lot in fiction with an incompetent coroner.

Things get more complicated if the shooting took place outside, or if (as sometimes happens) the slug went through a wall and exited outdoors. That's when it sometimes takes a careful search, using metal detectors if possible, to locate the slug. In that case, triangula-tion is especially important, as a line drawn from the final location of the slug through the hole in the wall can usually be extended to locate the exact spot from which the weapon was fired and, often, the height of the person who fired it as well.