Friday, 9 August 2013

Forensic Fridays Part Six: Bullet Wounds

This month in forensics we're talking Bullets! Good old fashion bullets. Let's get started.

From the Canadian Series "Murdoch Mysteries"

Firearms account for 32% and 60% of homicides in Canada and the United States respectively.

Gunshot wounds are separated into different categories based on range and type of weapon (caliber of bullet etc.)

·         Contact wounds appear when the gun is pressed against the skin when fired. A black, round wound will appear on loose skin (chest, abdomen) and may appear in areas where the skin is tighter against the skeleton like the head but bruises and stellate-shaped wounds can also appear. Soot often appears on contact wounds along with muzzle imprints and lacerations of the skin from the effects of gases.

·         Near contact is when the gun is held a short distance away from the skin. The wound that appears is black and circular.

·         Intermediate can appear from a variety of ranges but is marked by the stippling that appears around the entry wound caused by unburned powder causing pinpoint abrasions on the skin.

·         Distant also produces stippling and also round wounds with an abrasion ring on the surrounding skin. They will typically produce a hole roughly the caliber of the projectile fired.

·         In contact wounds to the head with center fire rifles, there is massive tissue damage to the skin, skull, and brain. Full metal jacketed bullets have less tissue damage and usually travel through the body undamaged. In half-jacketed bullets the jacket peels back as it travels through the body releasing several small lead fragments.

·         Shotgun shellscontain numerous pellets. At close range the entry wound is singular and round but as the range increases the central wound becomes smaller and the number of surrounding pellet holes becomes larger. The further away the weapon is when fired, the wider the spread of pellets, causing multiple entry wounds.

·         In flat bones like the skull, entry wounds are round and show internal beveling in which the inner table of the skull is more eroded than the outer producing a cone shape in the bullet’s path, sometimes carrying fragments of bone with it. Numerous fractures may also appear on the skull due to rapidly increasing pressure as the bullet travels through the skull. Bevelling can be used to determine the direction of the bullet passing through bone.

·         Shoring occurs in an entry wound when the bullet passes through a firm object before breaking the skin such as wood, glass, metal. Shoring produces as a greater wound diameter and greater marginal abrasions.

Exit wounds usually create an irregular shape and don’t show the same signs as entry wounds: muzzle imprints, stippling, black bruising, etc. They are typically larger than the entry wound and can also be numerous due to fragmentation. Entry wounds do not occur during every shooting. The bullet or projectile may remain inside the body or object that it hits.

Gun powder residue is a good way to distinguish between a Contact and a Distant wound through many factors:

1.       Firing distance

2.       Length and diameter of the firearm barrel

3.       Angle between the firearm barrel and the target

4.       Characteristics of the cartridge

5.       Environment (wind, rain, heat)

6.       Type of clothing

7.       Intermediate targets

Different types of guns use different calibres of bullet or even different types of projectiles eg shells.  These will leave different marks. Admittedly I know very little to absolutely nothing about guns so I’ll just leave this link here for you to read:

You can read the rest of the Forensic Friday series here:
  1. Body Decomposition
  2. Human Anatomy
  3. Blood Spatter
  4. Asphyxiation
  5. Stab Wounds

No comments:

Post a Comment