Firearms investigation

Question 1

How would you investigate a firearm? (2 step process)

Answer 1

• Conduct Pathology

- Investigating gun and bullets (Identifying gun from bullet and linking bullet to gun)

Question 2

What does pathology determine in firearms investigation?

Answer 2

-The type of gunshot wound
&
-The type of bullet which determines what gun was used (e.g. rifle or shotgun)

Question 3

What does the anatomy of a cartridge involve?

Answer 3

• Projectile
• Cartridge case
• Powder
• Primer

Question 4

How do you distinguish characteristic of guns?

Answer 4

• Rifling - grooves cut in barrel of rifle to give bullet spin
• Lands - metal peaks between rifling grooves (characteristic to each gun)
• Grooves - valleys between lands
• Calibre - diameter of gun barrel in inches (45 calibre = 0.45 inches diameter)

Question 5

How do you match a bullet to a gun?

Answer 5

• Identify the bullet impression using pattern matching
• Identify the bullet size to determine calibre of the gun
• Identify the bullet/cartridge serial number

Question 6

How do you visualise obliterated serial numbers?

Answer 6

• Use fine iron dust and sprinkle it onto the bullet/cartridge surface
• Iron dust attaches to magnetic field
• Serial number shows up

Question 7

How do you identify tool marks on a gun?

Answer 7

By using comparison microscopy

Question 8

What constitutes a bullet/gun match?

Answer 8

-Professional judgement - ‘sufficient agreement’

Question 9

How do you investigate a firearm?

Answer 9

• View down the barrel (shows the rifling and defects)

- Right-handed (clockwise twist)

Question 10

How do you investigate cartridges?

Answer 10

• Test fire using suspects gun

- Compare patterns with recovered cartridge/bullet (comparison microscopy)

Question 11

How do you carry out comparison microscopy?

Answer 11

By using a comparison microscope by test firing a cartridge and using the cartridge from the scene

Question 12

Where can gunshot residues be found?

Answer 12

• Hands
• Hair
• Clothing
• Furniture

Question 13

What chemicals are in gunshot residues?

Answer 13

• Components of bullet/cartridge e.g. lead
• Gunpowder
• Combustion/reaction products

Question 14

What part of the bullet would you find in a body?

Answer 14

Projectile (top of the bullet)

Question 15

Where would you find the primer?

Answer 15

On the ground (you can trace the serial number)

Question 16

What are the effects of firing: bullet impressions?

Answer 16

You may find ridges in the bullet, caused by the grooves

Impressions of the bullet caused by lands

Question 17

How do you analyse the components of a bullet?

Answer 17

1. Bombard bullet with electrons

2. Components will appear on a graph