BallisticsBallistics

YouTube - Bullets in Slowmo

BallisticsBallistics

The study of Ballistics involves the:

• Comparison of bullets and cartridge cases.

• Knowledge of all types of weapons.

• Restoration of serial numbers.

• Detection of gunpowder residue.

• Estimation of muzzle to target distance.

BallisticsBallistics

Comparison of Bullets and Cartridge Cases

• Guns have two basic categories:

Hand Guns

Colt .45 Automatic 1911 A1 Pistol

Rifles

.30 Caliber M1 Rifle

BallisticsBallistics

• In addition, guns can be “rifled” or “smooth bored” .

BallisticsBallistics

What is “rifling” and why is it necessary?

• Rifling is the machining of “lands” and “grooves” to the inside of the gun barrel.

• These cause the bullet to spin as it exits the gun barrel giving it stability and increased accuracy.

• Certain dimensions of this machining process give us the “caliber” which we are so familiar with.

BallisticsBallistics

• Bore – Is the distance from land to land.

• Lands – Is the area of the barrel not machined out when rifling.• Grooves – Is the spiral cut out of the barrel, “rifling”.

• Caliber – Is the distance between lands, inches or mm.

BallisticsBallistics

• What type of evidence is Bore, # of Land and Grooves, and Caliber? Class or Individual.

Answer: Class

Remember Class evidence is associated with a particular group. There are plenty of 9 mm Glock hand guns floating around.

• Can this particular 9 mm Glock hand gun become Individualized?

Answer: Yes

• After repeated firing the land and grooves become “marked” as the bullet travels in the barrel.

BallisticsBallistics

• These marking leave “striations” on bullets as they exit the barrel.

• Investigators can match bullets with specific guns by comparing these striations.

• It’s these striations which make each gun individualized. We can then say a particular bullet came from a specific gun.

BallisticsBallistics

• How do investigators get bullets for comparison?

• Ballistic Gel YouTube - Ballistic Gelatin

• Water Tank YouTube - PHY NYA Gun bullet in water tank

• Bullets are compared and investigators can determine if a bullet was shot by a particular gun.

BallisticsBallistics

• Can bullet casings be compared and linked to a specific gun?

Answer: Yes

• Just as the inside of a barrel leaves individual markings on bullets, the firing pin will leave individual markings on the cartridge.

• In each case, respectively, the bullets were fired by the same gun.

BallisticsBallistics

• Can investigators recover serial numbers from firearms?

Answer: Of course they can.

• By applying certain acids onto gun surface where the serial number has been “erased” or scratched away, serial numbers become visible again.

BallisticsBallistics

• Can Gunshot Residue (GSR) provide investigators with valuable information?

Answer: Do I need to answer this?.

O.K. Yes.

YouTube - Gun shot so slow you can see the bullet

• GunShot Residue is gun powder that does not burn when the bullet is fired.

BallisticsBallistics

• Gunshot Residue is ejected forward and backward, so the person firing the gun will have traces of the residue on his/her hand.

• This residue is easily detected and analyzed.

• Gunshot Residue can provide information about the muzzle to target distance.

BallisticsBallistics

• Because GSR leaves the muzzle in the shape of a cone, the diameter of the GSR left can give an indication of muzzle to target distance.

Point Blank 3” 9”

15” 21”

BallisticsBallistics

Bullet Trajectory and Path

• Since bullets obey the laws of physics it is easy to determine their origin and distance traveled.

• This can be done by using dowels or lasers.