For the December 2014 segment of Righting Crime
Fiction, I will continue talking about how you can use firearms evidence to
solve your fictional crimes that involve guns, with a focus on spent shell
casings and the link between casings and firearms.
FIRING PIN FINGERPRINTS
A bullet casing can be scarred in a number of
ways upon being fired and ejected from a firearm, but the most beneficial and
telling “scar” would be from the firing pin. When a firing pin strikes the
primer (on centerfire bullets) or the rim (on rimfire bullets), it leaves a
unique mark similar to a fingerprint. What happens is this: the firing pin
strikes every bullet it fires in the same way each and every time (unless there
is damage or some other change to the weapon), which leaves the exact same
imprint each and every time. This “fingerprint” left by the firing pin is
extremely helpful in determining if a particular firearm fired a particular bullet
casing.
CENTERFIRE VERSUS RIMFIRE
What’s the difference between centerfire and
rimfire? Quite simply, the firing pin on a centerfire weapon will strike the
center of the casing’s head (the primer), while the firing pin on a rimfire
weapon will strike the rim of the casing’s head (where the priming compound is
located). Most modern firearms are of the centerfire variety. However, there
are still numerous rimfire weapons available, many of which fire the very
popular .22 caliber bullet.
Plinkerton
.22 Caliber Single-Action Revolver
NOTE: The following two photographs demonstrate the
difference between a centerfire bullet and a rimfire bullet. In both photographs,
the unfired bullet is to the left and the spent shell casing is to the right.
Centerfire
Bullet/Casing
Rimfire
Bullet/Casing
LINKING THE SCENE TO THE GUN
If your detective only has spent casings in her
possession and no firearm to which she can compare them, the casings are nearly
useless. (They might make for a cool-looking necklace, but, other than the
benefits previously described in the November segment regarding caliber
identification, etc., they won’t help her solve her case.) Of course, there are
at least two ways to use the lone shell casings without an accompanying firearm
(I will discuss one in a later post and the other at the end of this section),
but in most cases it is imperative that she recover the firearm used in the commission
of the crime. In real criminal cases, we have to work with what we have and
there are many times when we are unable to recover the firearms used in the
crime. However, you control your fictional world and you can work out creative
ways for your detective to recover the firearm—unless it suits your story to
keep the firearm hidden.
With the casings and the firearm in her
possession, your detective is now ready to attempt to have the two linked together.
The first thing she would do is submit the spent casings and the firearm to the
lab. Once at the lab, these items may be processed for other evidence (DNA,
fingerprints, etc.) before the ballistics examination begins. When these other tasks
are completed, the firearms examiner can begin comparing the spent casings to
the firearm.
The examination is not carried out by directly
comparing the spent casings recovered at the scene to the suspected firearm.
Instead, the firearms examiner will compare the spent casings recovered at the
scene to a “known” spent casing fired from the firearm. In order to obtain this
“known” casing, the firearms examiner would test fire the firearm under
controlled conditions (usually by firing into a large water tank located at the
crime lab), and then compare the firing pin marks on the recovered shell
casings to the firing pin mark on the “known” casing by viewing them
side-by-side under a microscope. If these marks are the same, the firearms
examiner can conclude that the casings were fired from the same firearm. In
addition to these firing pin marks, or “fingerprints”, the examiner will search
for other unique “scars” left on the spent casings, such as the ejector or
extractor marks. These additional marks will aid the examiner in bolstering his
conclusion that the spent casings located at the crime scene were fired from
the firearm in question.
Now, when your detective links a spent shell
casing she recovered from a crime scene to a particular firearm, she has linked
the crime scene to that weapon. She must then link the firearm to the suspect,
and I will discuss that in a future post.
WHAT IF MY DETECTIVE DOES NOT HAVE A FIREARM?
If your detective does not have the suspected firearm
in her possession—as mentioned earlier—the casings are nearly useless. However,
certain casings can be entered into a database called IBIS (Integrated
Ballistics Identification System)/NIBIN (National Integrated Ballistic
Information Network), where they would be compared against other casings
recovered in connection with other crimes around the country. If the system
identifies two casings that are similar, a firearms examiner would then compare
the two to make a final determination. Now, this would indeed be a long shot,
and you should seek out more creative ways (I’ll discuss one in a future post) to
have your fictional detective link the casings to a particular firearm.
TRANSFERRING TO FICTION
Unless you are writing your story from the point
of view of a firearm’s examiner, you only need a very basic knowledge of the
examinations process, as described above. As a detective, I simply recovered my
evidence in the proper manner and submitted it to the crime lab utilizing
acceptable procedures (also to be discussed in a future post), and then I would
sit back and wait (doing other things on the same case or working new cases, of
course, but my work was done for the moment as far as that evidence was
concerned). I would later receive a report from the lab detailing their conclusions.
If more information was needed, I’d simply call the examiner and discuss his or
her findings.
In the following example from one of the first
short stories I ever wrote (A COLD MURDER, Detective
Mystery Stories Magazine, February 2004), the firearms examination takes
place off-page and the results are communicated in dialogue:
Cade
knelt outside the driver’s door of the truck and looked under the seat. There
was a Burger King bag and a couple of compact discs. He pulled the bag out and
something rolled across the floorboard and came to rest under the brake pedal.
He felt for the small object and, when his fingers found it, he knew instantly
what it was—a nine-millimeter shell casing.
“Les,
stand in front of the truck,” he said, excitement starting to course through
his veins. He stood outside the open driver’s door and pointed his finger at
Leslie. “If I’m shooting at you, my casings are gonna eject to the right and
back. Most of the casings will ricochet off the side of the truck and fall to
the ground, where we found them. But one—that missing one—found its way into
the truck. I’ll bet my left foot this is the casing that we couldn’t find at
the scene.”
Leslie
kept the Cassells preoccupied while Cade raced to the crime lab. He stopped
first at the firearm examiner’s office and then hurried down the hall to the
fingerprint lab. Within the hour he was back at the station house with the
results.
When
he and Leslie were seated in his office with Joseph Cassell, he held up the
casing and said, “You see this?”
Joseph
nodded.
“This
was found under the driver’s seat in your truck.”
“I
have lots of fired casings around the house and in my truck. When I go deer
hunting I usually throw my empties in the back of my truck. I clean them up
later. I must’ve missed that one.”
“You
hunt deer with a pistol?”
“No.
I have a nine millimeter carbine that I use.”
“Well,
this is a special casing.” Cade set it on the desk in front of Joseph. “This
casing matches four other casings that were found at the scene of Jeffery
Stokes’ murder. And that’s not all. We found Jeffery Stokes’ fingerprints on
the hood of your truck.”
Joseph
started in his chair. “Are you saying I did this?”
“If
you did, I wouldn’t blame you much. Had I just learned some sick pervert was
taking nude photos of my daughter—”
I’ve also worked actual cases
where the firearms examiner processed the evidence as I waited, and I detailed
such a scene in another of my early short stories titled A BADGE LIKE MINE (The Writer’s Hood, October 2003):
I drove to the crime lab and gave Willie
the chrome pistol. “Check this against the bullets from the Wilson murder . . .
I’ll wait.”
“Oh,
you want it done now?” Willie asked.
“Please.
It’s kind of important.”
Willie
took the pistol and fired it into a large water tank. The casing ejected from
the pistol and bounced off the wall and rolled under the tank. Willie fished
the projectile out the tank and asked me to get the casing from underneath. “My
back ain’t what it used to be,” he said.
I
had to use a broom to get it out and then handed it to Willie. He marked it and
then stabbed it onto a piece of clay opposite the casing that was recovered in
the Wilson murder. Muttering to himself, he hunched over his microscope and
turned this knob just so, adjusted that one a little, moved the casing ever so
slightly . . .
“Yep,”
he finally said. “This is a match.”
So, it’s as simple as that. You can have your
firearms examiner come to the conclusion that will move your story in the
direction you want it to go. Bear in
mind, though, that in the majority of real cases, firearms evidence will take
days, weeks, or even months to be processed at the lab, especially if
submitting to a state crime lab with a heavy workload. However, if you need
ballistics evidence to come in quickly for the sake of your story, that is also
realistic. I worked several murder cases where time was of grave importance and
the firearms examiner processed the evidence on the spot while I waited.
Well, that’s all for the December post, folks. I
wish all of you a happy, healthy and prosperous New Year filled with lots of
writing success.
Until then, write, rewrite, and get it right!
©BJ Bourg 2014
