What is this?
Forensic
Ballistics
 Analysis of bullet impacts to determine
the type.
 Firearm and tool mark examinations
involve analyzing firearm, ammunition,
and tool mark evidence in order to
establish whether a certain firearm or
tool was used in the commission of a
crime
 Ballistic experiments have been with us since
ancient times, when war machines were
slinging rocks over the walls of fortified
towns. As a science it began with the study of
flight-paths when shooting at targets.
 One of the first to apply the science of
ballistics to criminology was Eugene Francois
Vidocq, the first head of the French Sûreté.
The modern ballistics expert is concerned
with three areas:
1. Internal ballistics: what happens inside a weapon when it
is fired.
a. Firing pin makes a distinct mark on the cartridge.
b. Explosive pressure causes the bullet to expand
slightly to fill the spiral 'rifling' grooves cut in the
bore.
c. Then the bullet spins as it passes down the barrel, but
it leaves tell-tale marks on the bullet that are unique
to that particular firearm.
* The presence of rust or spider silk indicates the gun has not
been fired recently.
* At close range, particles from a wound may lodge inside the
barrel.
2. External ballistics: what happens to the bullet
and residues outside the gun, including the
direction and velocity of the shot, as well as any
deviation in the trajectory.
3.
Terminal ballistics Studies changes in
trajectory and speed caused by ricochet and
penetration of objects, and layered deposits
on parts of the bullet accumulated as it
contacts these objects.
Includes examination of wound shape and
extent of tissue damage. If a bullet cannot be
removed for examination, its caliber can be
measured by CT scanning.
Forensic Ballistics: the scientific analysis or
interpretation of all ballistic related evidence and
phenomenon with the sole purpose of interpreting
or establishing the true facts in a shooting related
incident.
Ballistic related evidence includes: firearms, bullets,
and cartridge cases.
However a listing of Ballistic related phenomenon is
endless, including: bullet holes, bullet damage on
various mediums; bullet trajectories, and gunshot
wounds.
Method to find the gun used in a crime
by matching the bullet's striations (or
striae) with the rifled barrel through
which it was fired, or by matching marks
on the cartridge case to marks in the
chamber and breech.
Application of toolmark
identification.
Ballistics Terms to Know:
 Ballistics: the study of bullets and firearms
 Barrel: the long, metal tube that guides a
projectile out of a firearm
 Breech: end of barrel
attached to firing mechanism
of a firearm where the
cartridge is loaded and
unloaded
 Bullet: the projectile that is
sent flying when a firearm is
shot
 Caliber a measure of the inside diameter of
a firearm barrel
 Cartridge a case that holds a bullet, primer
powder, and gunpowder
 Firearm a weapon capable of
firing a projectile using a
confined explosive as a
propellant
 Fully automatic: a firearm
with a clip fed mechanism that
fires repeatedly as long as the
trigger is pressed
Gunshot Residue: (GSR) the tiny particles expelled
from a firearm when it is fired. A.K.A trace evidence
 chemists have developed a reliable new test
for detecting the presence of gun shot residue.
Above is a residue particle -- roughly 1/20 the
size of a period -- that has been magnified 200
times with a digital microscope
 Lands and Grooves: ridges (lands) and depressions
(grooves) found on the inside of a firearm’s barrel
that are created when the firearm is
manufactured.
 Muzzle the end of the barrel where the projectile
exits a firearm
 Pistol a hand-held firearm
 Revolver: a pistol with a revolving cylinder
 Rifle a firearm that has a long barrel, a long
gun
 Rifling the spiral pattern of lands and grooves
in the barrel of a firearm
 Differences Between Rifles,
Shotguns, and Handguns
 Rifle Scopes
 Semiautomatic a pistol with a clip-fed
mechanism that fires one shot per pull of
the trigger; the empty cartridge ejects and
the next cartridge advances automatically
 Shell casing: the metal (usually brass)
housing for the gunpowder of a
firearm
 Trajectory: the path of flight of a
projectile
Ballistics are a branch of criminalistics in forensic
science.
Education and Training:
The minimum requirement is a bachelor's degree in
chemistry, biology, physics, molecular biology, or a
related science.
In the future, a master’s degree may be required. Many
colleges and universities offer degrees and courses in
forensic science. In deciding whether to get a degree in
chemistry or biology, or one in forensic science, study the
courses offered.
At least 24 semester hours of either chemistry or biology
is required and math is a must. The title of the degree is
not as important as the courses taken.
You need to be good in math and science, and have
knowledge of firearms.
It can be rewarding job, knowing that with your help, you
can find out the type of gun that a bullet came from, that
may have hurt or killed someone.
That would be a relatively easy problem to solve,
compared to trying to figure out the angle and velocity of
a bullet to have to hit a target when trying to find out if a
person standing at point A could have possibly hit
something or someone standing at point B.
 To keep up with the many advances in science,
criminalists must take continuing education
courses all during their career. By passing a
difficult examination, they may become certified
by the American Board of Criminalistics
(www.criminalistics.com/ABC).
 Entire forensic laboratories may prove their
competence by becoming accredited by
organizations such as the American Society of
Crime Laboratory Directors/Laboratory
Accreditation Board (www.ascld.org/lab).
 ~http://www.aafs.org/employ/brochure1.htm#Cr
iminalistics
How bullet imbalance causes a lateral drift
velocity which causes deflection of the bullet
trajectory as it leaves the muzzle.
http://home.snafu.de/l.moeller/Geschosse/Bullet_Imbalance.html
The left sketch shows how the Center of
Gravity (CG), offset from the center line or
geometric axis, is forced to rotate about the
geometric axis.
This is an unnatural condition. A spinning projectile will
always spin about its principal axis and the principal axis
always passes through the projectile CG. Consequently,
when it exits the muzzle, it will start to spin about its
principal axis and CG.
While the bullet is in the bore, the CG offset produces a
tangential velocity component (Vt). When it exits the
bore, this Vt will as a Vd be maintained.
The lateral drift velocity will be perpendicular to the
plane containing both the geometric and principal axes
at the instant of muzzle exit, obtained the distance, that
the bullet will deflect, by multiplying the lateral drift
velocity by the flight time (FT).
The equation that calculates the amount of bullet
deflection at the target is:
  24 (V / t )( FT )
  bullet deflection in inches, radius of dispersion or miss distance
  3.14159
V  velocity at the muzzle infps. Note that V is about
50 to 100 fps. less than the instrumental velocity(2900fps).
This results from the muzzle blast continuing to accelerate
the bullet after it leaves the bore.
t  twist rate in inches per revolution (10 in.)
FT  Time of Flight (0.1 second at 100 yards)
  CG offset in inches
http://home.snafu.de/l.moeller/Geschosse/Bullet_Imbalance.html
This figure shows 4 3-shot groups formed by indexing the bullets in 90
degree increments in roll angle. The bullets had a large CG offset c’0.00118
in. The experiment determined the radius of dispersion at 100 yards was
about 2.5 inches.
http://home.snafu.de/l.moeller/Geschosse/Bullet_Imbalance.html
This CG offset value was determined by the
diameter and length of the hole drilled in the
side of the Bullet, used in the experiment that
follows. Let's calculate the dispersion radius to
be expected at 100 yards from this oversize CG
offset.
 = 24*3.14159*(2900/10)*0.1*0.00118 = 2.58 inches
Gravity vs. the bullets velocity and spin…
Then… if there is wind…