Medico Legal Module
21 st Batch
June 2014
Dr. Sanjaya Hulathduwa
MBBS, MD, DLM, DMJ Path(Lond)
DMJ Clin(Lond) , Dip. Crim, MFFLM(UK)
Senior Lecturer

Firearm - a device designed to propel a projectile through a cylinder/ barrel.
The force needed for the propulsion of the projectile is usually generated by the pressurized gas produced by the combustion of a small amount of explosive material known as propellant in an enclosed space.

It is a general term to denote cartridges, grenades, mines, rockets and artillery.
‘complete round used for firing after insertion in to a barrel ‘.

Smooth bore weapon cartridge is usually consisted of a case with a metal base, propellant, projectile (shot), cap/primer and wads. The shot usually consists of multiple metal balls.
Rifled bore weapon cartridge is made of metal alone. The two main components of the cartridge are the bullet (the projectile) and the case.
The rifled bore weapon cartridge has a length
(height) and a caliber/ bore.

1. Smooth bore weapons
2. Rifled bore weapons

Types of Smooth Bore Weapons seen in Sri Lanka
1.
Breech loading shot gun
2.
Breech loading shot pistol
3.
Muzzle loading shot gun
4.
Muzzle loading trap gun (‘ Kandan thuwakkuwa’, ‘maruwela’, bandina thuwakkakuwa ’) – A country made shot gun
5.
Muzzle loading shot pistols
6.
Swan-off shot gun (‘ Galkatas ’) – An improvised modification of shot gun

A shot gun could be a muzzle loader or a breech loader.
Muzzle loader
Ammunitions do not come in a compact form.
Components of a shot should be refilled before each shot
Breech loader
Ammunition is always a standard factory made (shot gun cartridge).

A shot gun is of two types
 Single barreled
 Double barreled
When double barreled, they are usually positioned side by side or rarely one below the other.

A rifled weapon has a barrel with multiple fine grooves which make the bullet to spin around its own axis when it leaves.
This gyroscopic movement will minimize the wobbling of the bullet enabling it to keep its track to find the target thus enhances the accuracy.

1. Revolvers
2. Self – loading pistols (semi automatics)
3. Sub machine guns
4. Machine guns
5. Self – loading rifles (SLR)
6. Snipers

A firearm injury is usually a perforating laceration.
The identification of an injury as a firearm injury is based on the following criteria; a. Familiarity b. There is an entry, track and an exit.
c. The characteristic features of a firearm injury - abrasion collar, burning, blackening and tattooing may be present.
d. The history by eye witness – circumstantial evidence

 A bullet or a collection of pellets (shot)
 Wads (if available)
 Residue of primer (burnt, partially burnt and unburnt)
 Residue of propellant (burnt, partially burnt and unburnt)
 Residue lubricants
 Fowling present in the barrel due to previous shot
 Compressed gas containing soot
 Flame
 Heat
 Noise

• Is it a firearm injury or not?
• If it is a fire arm injury, what is the nature of the firearm and ammunition?
• How many fire arms have been used?
• How many shots have been fired?

• What is the sequence and direction of firing?
• What are the circumstances? Are they accidental, suicidal, homicidal or done in self defense ?
• Recovery of spent cartridges and other trace material from the scene.
• Have the spent cartridges been shot from this specific gun? (Specific identity of the weapon)
• Identity of the assailant.

• Identity of the deceased.
• Identity of the entry, the path inside the body and respective exit wounds.
• The cause of death
• Time since death
• Possibility of volitional activity.
• Reconstruction of the event.
• Approximate distance of firing.

Entry Wounds and Exit Wounds
Entry Wounds
• Usually smaller, circular or oval (approximately the size of the missile)
• Abrasion collar and contusion collar are present.
• Burning, blackening and tattooing may be present.
• Muzzle mark may be present.
• Margins are inverted.
• Clothes are driven inward in the track.
• Pinkish discolouration of the wound may be present due to Carbon monoxide.
• Beveling of the inner table of the skull.

Exit Wounds
• Typically large and irregular. (but could be smaller. Ex: in contact and near contact entries)
• Abrasion collar absent.
• Burning, blackening and tattooing absent.
• No muzzle mark.
• Margins everted.
• Tissues from the track protruding out.
• No carbon monoxide.
• Beveling of the outer table of the skull.

Range of Fire
Smooth Bore Weapons
Contact range – Muzzle mark on the skin around the entry wound. Burning, blackening and tattooing with pink discolouration (cherry pink colour due to CO).
Near contact – No muzzle mark but with evidence of local explosive effect and burning, blackening and tattooing.
Within 1 foot – single entry with burning, blackening and tattooing.
Within 2 feet – single entry with blackening and tattooing only.
Within 3 feet (1 yard) – single entry with tattooing only.
Beyond 3 feet – tattooing is absent and the dispersion of the pellets begin and there will be individual entries caused by the dispersing pellets either singly or in combination.

Rifled Weapons
Contact range - Muzzle mark on the skin around the entry wound. Burning, blackening and tattooing with pink discolouration.
Near contact – No muzzle mark but with evidence of local explosive effect and burning, blackening and tattooing.
Within 6 to 12 inches - Burning, blackening and tattooing.
12 to 18 inches – Blackening and tattooing only.
18 to 24 inches – Tattooing only.
Beyond 24 inches – Tattooing absent.
Extreme ranges – The entry is large and ragged.

Direction of Fire
The direction of fire can be determined by the following factors.
The shape of abrasion collar, contusion collar, burning, blackening and tattooing;
Circular –fired at right angle
Elliptical – fired at an angle
The beveling of the skull;
Equal on all sides – fired at right angle
More on one side – fired at an angle
Shelving and undercutting are seen when fired at an angle.

Circumstances of Fire
• Homicidal
• Suicidal
• Accidental

Suicide Homicide
Usually single injury (may be multiple) with one fatal injury.
Multiple injuries on various parts of the body with more than one fatal injury.
Weapon found close to the body usually gripped in hand in cadaveric spasm.
Weapons not found with the body or the surroundings.
Entry wounds are found in accessible sites.
Entry wounds can be at any place of the body.
Not an elective site.
Entry wound in an elective site such as temple, mid forehead, roof of mouth, under the chin, precordium.
Range always contact or near contact unless a mechanism is used to pull the trigger.
Associated with psychiatric disturbances and previous para- suicidal attempts.
Usually no eye witnesses.
Range beyond arms reach (distant range)
Associated with enmity, robbery, rivalry etc.
Eye witnesses’ accounts

Medico legal investigation
• History – reference to type of gun, number of shots, range and relative positions of victim and assailant.
• Visit to the scene
• Identification of the body
• Preliminary procedures
Photography
X – rays

• Collection of trace materials
(missiles and wads, soot, burnt and unburnt gunpowder from the clothing and the entry wounds, gun powder from the hands of the weapon-user -useful in suicidal firearm injuries)
• Clothing – for burns, powder residues and infrared photography
• General external examination
• Specific external examination – entry and exit wounds
• Internal examination (track including injuries to internal organs and tissues/ recovery of pellets, bullets wads etc.)
• Laboratory investigations by the Forensic Ballistics expert
• Documentation and reporting