Forensics- Ballistics

What important event for ballistics happened in 1375?

• the first ever gun was created → for hunting

What important event for ballistics happened in 1498?

• rifling was invented

What important event for ballistics happened in 1835?

• 1st Ballistic Case

  • Blacksmith’s had to put marks on the bullets they made, and hthat mark was used to help solve a homicide case

What important event for ballistics happened in 1879?

• rifling marks in a barrel are used in court to help differentiate 2 revolvers from each other

What important event for ballistics happened in 1925?

• the comparison microscope was created

What is the most important takeaway from the “Theory of Firearm Identification?”

• all firearms are unique

Why was rifling invented?

• to make the bullet travel faster and be more accurate

What are the 4 pieces of class evidence that are cut into the rifling pattern?

1. caliber

2. # of lands and grooves

3. width of lands and grooves

4. direction of the twist

What does a land inside the barrel of the gun leave on a bullet fired from that gun?

• Striations

What are striations?

• special marks found in the groove of a bullet

• as unique as fingerprints

What is the major difference between a semi-automatic and an automatic gun?

• Semi-automatic: press the trigger multiple times

• Automatic: press and hold the trigger

Which part of the firearm keeps the spent cartridge from coming back and hitting the shooter?

• breechface

What is centerfire ammunition?

• when the firing pin hits the center of the headstamp

What is rimfire ammunition?

• when the firing pin hits the edge of the headstamp

What does the ejector do and where are the marks it leaves?

• removes the spent casing from the weapon

• on the outer-edge of the back of the casing

What does the extractor do and where are the marks it leaves?

• loads a new cartridge into the weapon

• on the side

What does the firing pin strike to ignite the gunpowder?

• the primer

What is single-action for revolvers?

1. cocking the handgun back

2. pulling the trigger

What is double-action for revolvers?

1. pull the trigger

What part of the revolver are the bullets loaded into?

The cylinder

What are typical bullets made out of?

• lead

What are the benefits of using lead as a bullet material?

• the material is easy to access

• soft

• heavy

Once a bullet hits its target its shape will deform/fragment. What is this bullet now called?

• slug

What does it mean for a bullet to “fragment?”

• to break into pieces

What design feature allows rifle ammunition to be more powerful?

• bottleneck cartridge

Which part of the shotgun ammunition holds the shot in place inside the shell?

• wadding

How is caliber calculated?

• find the width of the barrel/base of the bullet

• measured in in and mm

What happens to the power of weapon when the caliber increases?

the power increases

How is gauge calculated?

• how many lead bullets are needed to make 1lb of lead per the barrels diameter

What happens to the power of a weapon when the gauge increases?

• the power decreases

How wide is the headstamp of a 38 caliber ammunition?

• .38 in

What is a fully jacketed bullet?

• a bullet that is completely covered by a hard metal

  • commonly copper

• designed to travel deeper, less destructive, and a small path of destruction

What is a semi-jacketed bullet?

• a bullet that is covered in a hard metal, but the nose/tip is left uncovered

• designed to deform, travel deep, and a large path of destruction

What is a hollow point bullet?

• a semi-jacketed bullet, but the nose is hollowed out

• designed to fragment, travel deep, and create multiple paths of destruction

What will rifling leave on a fired bullet? It is also known to be individual evidence that can be observed under a comparison microscope.

• striations

What is gun shot residue (GSR)?

• particulate matter that is released from the firearm when the trigger is pulled

Where will you find GSR?

• anywhere in a 2ft radius around where the gun was fired

  • ex: on the shooter’s hand, arm, clothes, and shoes

    • can also fall onto the victim, if they were that close

What is the Griess Test?

• a chemical test that is used to find GSR

• only lasts 4-6 hours

• the reaction is orange/red

What characteristics of a gunshot wound would indicate that the shooter held the weapon more than 2ft from the victim?

• an abrasion collar

  • a bruise around the bullet hole

  • bullet hole is a perfect circle

What characteristics of a gunshot wound would indicate that the shooter held the weapon between 6in and 2ft from the victim?

• stippling

  • bruises from the GSR

    • the GSR has time to spread onto the skin

What characteristics of a gunshot wound would indicate that the shooter held the weapon between 1in and 6in from the victim?

• bloody stippling

  • the GSR had broken skin

    • less spread since the GSR is so close to the skin

What characteristics of a gunshot wound would indicate that the shooter held the weapon point-blank?

• stellate

  • a star-like shape, since the energy of the gun is transferred through the skin

  • the skin is broken/ torn

What are the 2 types of firing pins?

• rectangular

• hemispherical

What are the 3 types of breech face?

• parallel

• arched

• circular

  • found on a spent casing

What are the 4 pieces of individual evidence left on a spent casing?

1. breech face

2. ejector marks

3. firing pin impression

4. extractor marks

What type of tool is used to see and compare extremely small marks left in bullets and casings?

• a comparison microscope