1. Ballistic Evidence

2. Ballistics Ballistics  the study of bullets and firearms
Firearm  a weapon, such as a gun, capable of firing a projectile using a confined explosive

3. Firearms History Matchlock weapons Flintlock weapons
 Relied on wicks to carry a flame to the gunpowder
Flintlock weapons
Relied on sparks from a piece of flint to ignite the gunpowder
Could be used in damp weather
Percussion weapons
Introduction of cartridges (a casing that holds a bullet)

4. Gun Parts – The Barrel
Barrel of a gun is produced from a single rod of steel that has been drilled through the center
Drill markings are different for each type of gun produced
IE. Shotgun barrels are different than a rifle barrel
Have different purposes
Can vary in length
No two rifled barrels, even those manufactured in succession, will have identical striation markings

5. Barrel Manufacturers also impress the barrel with spiral grooves
 Known as rifling
The surfaces of the original bore remaining between the grooves are called lands

8. Barrel
Each gun manufacturer uses its own technique and own signature amount of lands and grooves
Ex. Smith and Wesson uses five lands and grooves twisted to the right

9. Caliber
Caliber of a rifle or handgun is the diameter of the gun barrel
Usually recorded in hundredths of an inch or in millimeters
Shotguns are measured by gauges

10. Hammer
Part of the gun that is responsible for beginning the reaction of a bullet firing is the hammer

11. Breechblock / Ejector Breechblock Ejector
The rear part of the firearm barrel
Stops the bullet casing from flying through the back of the gun
Ejector
Spits out the empty shell casings to make room for the next bullet

12. Bullet / Ammunition
Bullet is a combination of a gunpowder and a projectile
Can be a single bullet or can be hundreds of buckshot
Back of the bullet contains a firing pin that once struck, ignites the gun powder

13. Bullet

14. How A Firearm Works A Review
Pull the trigger and the firing pin of the firearm hits the base of the cartridge, igniting the gunpowder mixture
Gases expand and bullet is propelled forward and case is forced backward
Bullet is expelled through the barrel – spinning according to the land and groove pattern. The spent casing is ejected from the rear of the gun.

15. Bullet projection
As soon as the explosion occurs, the bullet is expelled out through the barrel of the gun
Bullet is spinning
This is due to the lands and groves in the barrel
This creates markings on the bullet

16. Opposite Reaction
Bullet casing is forced backwards against the breechblock
Casing is the removed via the ejector

17. Casing Imprints
Casings are indented with the markings from the weapon’s firing and loading mechanisms:
Hammer
Breechblock
Ejector/extractor

18. Questions to Answer What type of firearm was used?
What was the caliber of the bullet?
How many bullets were fired?
Where was the shooter standing?
What was the angle of impact?
Has the firearm been used in a previous crime?

19. Critical Firearms Evidence
All of the items below are essential in firearms investigation
The bullet
The weapon
The serial numbers on the weapon
The gunpowder on garments, around wounds, and on hands

20. The Weapon
Safety is of the utmost importance when collecting the weapon
When collecting a found weapon, it is best to pick it up by the edges of the trigger guard or by the checkered portion of the grip

21. Weapon Comparison
Once a gun is collected, a test firing is completed in water to provide a point of comparison for evidence collected with the crime
Remember each weapon will leave its own unique markings on the ammunition that it is using (both bullet and casing)

23. Weapon Serial Numbers
Each weapon has a serial number associated with it
Used for registration and purchasing reasons
Criminalists can track movement of weapons based on serial number
Most of the time, criminals try to remove the serial number
Stamped serial numbers put stress on the metal of the gun
When an etching agent is poured on area, the stressed areas dissolve faster than surrounding metal and reveal the serial number

24. Collecting A Bullet
If a bullet is found lodged in something, it is best to remove the surrounding material as to not disturb any of the striations made
Investigator puts initials on nose or back of bullet
Wraps it in tissue paper to avoid scratching during transfer

25. NIBIN National Integrated Ballistics Network
Combination of NIBIS and Drugfire
United in 2000
NIBIN networks allows ballistics identification to be conducted on a local, national, or international scale.
This networking feature has been employed to successfully link crimes between countries.

26. Measuring Distance
In cases where a victim has suffered a gunshot wound, it is important to determine the distance from weapon to victim / identify the location of the shooter
Distance is determined primarily by the presence and distribution of certain powder patterns or by the spread of a shot (for a shotgun)

27. Gunshot Residue (GSR)
Primers in the bullet contain a blend of different chemicals
Look for the elements Antimony and Barium

28. Firearm Discharge
When a firearm is discharged, unburned and partially burned particles of gunpowder (in addition to smoke) are propelled out of the barrel, along with the bullet, towards the target
It is the distribution of gunpowder particles and other discharge residues around the bullet hole that permits an assessment of the distance from weapon to target

29. Gunpowder Distribution Factors
Factors that influence gunpowder residue on the target:
Barrel length
Caliber
Type of ammunition
Type and condition of weapon fired
Distance from weapon to target
No GSR will be on target if further than 3 feet

30. Gunshot Residue Distribution
Handling of a used firearm, the passage of time, and the resumption of normal activities following a shooting, gun shot residue is usually redistributed to other areas
Becomes harder to trace back to original weapon

31. Bullet Wipe
Dark ring around the perimeter of the entrance hole in a target
Consists of a mixture of carbon, dirt, lubricant, primer residue, and lead being wiped off of the bullet

32. Gunshot Residue Detection
Swab both the firing and nonfiring hand with a 5% solution of nitric acid or
Use adhesive tape on the hands to pick up the particles of residue
Tape is put under scanning electron microscope
More specific than hand swabbing

33. GSR Detection
Infrared photography – used to help find GSR in difficult situations (dark clothing or bloody clothing)
Greiss test  chemical test to develop patterns of GSR around bullet holes
Photopaper is ironed over entrance area
Paper is sprayed with chemical
Turns GSR pink then blue-violet