ballistics/explosives

Identify 5 firearm types

12 gauge shotgun, lever-action rifle, pistol, automatic, semi-automatic, revolver, bolt-action rifle

What is the purpose of rifling?

To make the projectile (bullet) spin when it is fired

What are lands and grooves and what are their purposes?

The raised and lowered portions of the barrel that create rifling and help improve shot accuracy

Identify 5 common calibers

.22, .25, .357, .38, .44, .45, 9mm

How does a firearm work?

The firing pin strikes the cartridge base, igniting the primer; the primer ignites the main propellant; expanding gas pressure pushes the bullet from the casing into the barrel; the bullet follows the lands and grooves and exits the barrel

What is the job of the cartridge?

To hold the primer, propellant (gunpowder), and bullet

What is the job of the firing pin?

To ignite the primer by striking the cartridge base

What are some things that can be used as a reference point for bullet trajectory?

An exit wound, a bullet hole in a wall, gunshot residue (GSR)

Identify 3 class characteristics compared among firearms

Number of lands and grooves, width of lands and grooves, depth of lands and grooves (also pitch and twist)

The caliber of a bullet usually matches its?

Diameter

How are bullets used for individual evidence?

Striations on the bullet are compared to the lands and grooves of a suspect firearm

Identify 3 cartridge case class characteristics

Manufacturer, shape, caliber (and composition)

Identify 3 cartridge case individual characteristics

Firing pin impressions, breech face marks, ejector marks (and extractor marks)

Give 2 examples of breech markings

Firing pin impressions and breech face marks

Identify 6 extracting pin and ejector marks

Extractor marks, ejector marks, rim nicks, extractor claw marks, ejection port marks, ejector rod marks

What can be determined by examining GSR patterns?

The distance between the shooter and the victim

Give 2 examples of reference points that could be used to calculate trajectory and explain how they calculate

Bullet holes in objects and entry/exit points on a victim; using those points with right triangle geometry determines the shooter's line of fire

When calculating trajectory, you know the distance where the shooter was believed to be and the angle of elevation. What can be determined from this information?

The height of the shooter

Which side of a bullet wound is typically larger?

The exit wound

What type of reaction is an explosion?

Combustion

Compare and contrast low and high explosives. Include detonation velocity and an example of each.

Low explosives: lower detonation/deflagration velocity around 3,000 fps, burn by rapid combustion, typically mixtures of fuel and oxidizer like black powder or smokeless powder. High explosives: much higher detonation velocity (often around or above 10,000 fps), contain oxygen within the molecule, include initiating (primary) and non-initiating (secondary) types; examples of secondary high explosives are TNT and PETN

What type of explosion would PETN produce?

Non-initiating (a secondary high explosive that requires a detonator)

Identify 2 methods used in the analysis of explosives.

Microscopy and thin layer chromatography (also infrared spectroscopy and analysis of detonator fragments)

Identify 10 areas of forensic science that have been used to investigate acts of terrorism.

Anthropology, DNA, serology, odontology, pathology, entomology, trace evidence, questioned documents, fingerprints, tools and toolmarks, engineering