Forensic Medicine

1. Forensic Ballistics
Dr Nikita Prabhakaran
Assistant professor

2. Ballistics
• It is the study of firearms and ammunition

3. Forensic Ballistics
• Deals with
1. the investigation of firearms and ammunition
2. Injuries caused by it and
3. the medico-legal problems associated with it

4. Internal ballistics External ballistics
Operation of a firearm and
the movement of the
projectile
Inside the firearm
Study of events
-after the discharge of the
projectile from the firearm
- Till it reaches the target

5. Terminal ballistics vs wound ballistics
• Terminal ballistics motion of the projectile
in the target
• Wound ballistics study of the injury caused

6. Parts of a firearm

7. Chamber, taper and bore

8. • Cartridge  pre-assembled firearm
ammunition
• Magazine- ammunition storage and feeding
device for a repeating firearm

9. Types of firearms
• Rifled firearms
• Smooth bore firearm

11. Rifling
• The internal surface of the barrel has been
scored by a number of spiral grooves
• More common number is 6
• Sometimes there can be microridges
• Projectile is usually called a bullet

13. • Examples are REVOLVERS
RIFLES
PISTOLS

14. • Projecting ridges are called lands
• The deep portions are called grooves
• Distance between diagonally opposite lands is
called calibre

16. • In USA it is measured in Inches 0.22
• In Europe expressed in millimetres

17. Need for rifling???
• Spinning action to the bullet
• Stabilizes its flight/ straight trajectory path
• Prevents wobbling/ tumbling
• Penetrative power increased
• Increases accuracy and range (NEET PG)

18. How to increase the range of firing??
• By increasing the length of the barrel
• So according to that :
– (a) Short barrel firearms
– (b) Long barrel firearms

19. Pistols and revolvers
• Short barrelled rifled firearm

20. Pistols
Catridges in a vertical magazine
When fired, empty catridge case
falls at some distance away
New catridge slips into the
breach automatically by spring action
Should be reloaded again
Hence, “ Semi-automatic”

21. Revolvers
• In a metallic revolving cylinder
• After firing, the cases remain there
• After one round, it should be loaded manually
again

22. • AK47
• AK 74
• Automatic rifles fire using gases of the
previous

23. SHOT GUN
• Single barrelled/ double barelled
• Smooth bored weapons
• Projectile- pellets

24. Bullet vs pellets

25. Choking???
• Reduction of diameter at the muzzle end of
the barrel.
• Reduces the dispersion of pellets and holds
the pellets together for a longer distance
• Can be non- choke bore/ choke-bore

27. Paradox guns
• Actually shots guns
• But with rifling at the muzzle end

28. GUAGE
• Indicates the diameter of the barrel
• Determined by no: of lead pellets which can
be made from one pound of pure lead
• Exactly fitting the bore of the shotgun

29. • Smaller the gauge  greater the diameter
• Ranges from 10 to 28.

30. CATRIDGE
• Consists of a metallic case in which:
• Projectile pellet/bullet
• Propellant gunpowder
• Primer gives the impulsive spark to ignite
the propellant

32. Functioning??
• Pulling the trigger and released
• Striker goes and hits the percussion cap
• Releases heat
• Primer inside the percussion cap ignites
• Explodes the gunpowder (propellant)
• Projectile is propelled

33. Purpose of wad??
• Plastic/ paper disc
• Acts like a piston
• Propells the pellets together

34. Primary marking and secondary
marking
• In all rifled firearms,
• Cartridges are usually larger than the barrel
• (for perfect obturation)

35. • Thus when a bullet passes through it,
• the markings of the lands on the bullet 
–PRIMARY MARKINGS
–Reveal the manufacturer of the gun
• Unique markings typical to the weapon
–SECONDARY MARKINGS

36. Projectiles

37. Pellets???
• Lead large pellets  buckshot/ mould shot
• Single large pellet in shot gun is called SLUG
• Smaller than bore diameter
• Base- hollow
• End-pointed

38. Bullet???
• Are of different sizes and shapes
• Varies from one firearm to another

39. Dum-dum bullet
• It is open at the nose and is covered with a
lead jacket.
• It expands on hitting the target
• Hence produces a larger wound

40. Frangible bullets
• They break into multiple pieces when they
enter the body
• Here, matching with the test bullet is difficult

41. Tandem bullets (Piggy tail/
piggy back bullet)
• It means two bullets come out from a single firing
shot
• Causes:
• (a) defective ammunition where one gets stuck
in the barrel and on subsequent firing the new
bullet comes along with the previous one
• (b) duplex/ tandem catridge manufactured in a
single catridge there will be two bullets one
behind the other

42. MLI
One entrance wound and two exit wounds
Or
Two entrance wounds
Or
No exit wounds

43. Ricochet bullet
• Bullet changes its direction by striking on
some surface or object
Bullets can get deformed
Speed is dampened and hence placed superficial
on the body

44. Types
• External ricochet
• Strikes an intermediate object before entering the body
• Entrance wound may be deformed
• May show foreign bodies from the striking object
• Usually in inferior weapons

45. • Internal ricochet
– Occurs inside the body

46. Medico-legal significance
• In case of external ricochet, unintentional
firing may be used as a defence
• The entrance wound will be larger than the
expected
• Velocity is reduced and may produce a
keyhole injury on the skull
• Gutter fracture on the skull
• Grossly deformed, identification is difficult.

47. Souvenair bullet
• Bullets remain in the body silently
• Sometimes, they are made to remain like that
• Because intervention might cause more
damage.
• Seen encapsulated by fibrous tissue.
• c/c lead poisoning may be seen.

49. Gun powder (Propellant)
• Black powder- classic one
• Smokeless powder
• Semi-smokeless powder

50. Black powder
• Potassium Nitrate (75%)
gives oxygen for burning
• Charcoal (15%) fuel
• Sulphur helps in ignition
• Coarse /fine FG, FFG, FFFG
• 1gm 3000 -4000cc
• CO, CO2, N2, H2S

51. Smokeless powder
• Single base- Nitrocellulose
• Double base- Nitrocellulose (60%)
• Nitroglycerine (40%)
• 1gm  12,000 to 13,000 gas

52. Semi- smokeless powder
• 80% black powder
• 20 % smokeless powder
• Triple baser Nitrocellulose+ nitroglycerine+
Nitroguanidine

53. Wounds produced by Firearms

54. In any firearm injury, there will be
(1)Entrance wound
(2)Exit wound
(3)Track of the fire-arm inside the body

55. Classification
• 1. Wounds caused by shotgun
• 2. Wounds caused by rifled firearms

56. Flame = 30 cm Smoke= 45 cm
Unburnt gun powder=
60 to 80cm

57. Wounds caused by shotgun
Product of firing Distance up to
which it travels
Injury caused
Flame 30 cm Burning
Smoke 45 cm Blackening
Unburnt powder grains 60-80 cm Tattooing
Pellets move together Up to 2 metre Single hole
Pellets spread >2 metre Multiple holes
Wad travel Up to 5metres
Metallic fouling due to metals expelled by the discharge

60. Wiping ++
• Tattooing  doesn’t go
• Smudging/blackening  goes off
• Metal fouling  does not go

61. Contact shot
• Explosive injury + Gross destruction of tissues
• Entrance wound:
• Muzzle imprint + Cherry red discoloration
• Burning, smoke and soot inside the track

62. Specific appearance of Contact Shot
• Muzzle/ recoil imprint mark
• Back spatter
• Blowback phenomenon or blast effect-
– Cruciate/ stellate/ragged laceration
– Especially if there is a bone underneath

63. • Clothes were present soot and burns on the
clothes +++
• Exit wounds- depends on the area of injury
• If its head, lesser space for the gas to
expand hence mutilated
• If it is chest or abdomen, a round entry wound
and an exit wound may be there

66. Close range < 30 cm
• Large entrance wound
• Burns singeing of hair
• Blackening / smudging due to smoke
• Tattooing in the periphery

67. 30- 45 cm range
• No burning
• Blackening and tattooing

68. > 45 cm - 80cm
• Only tattooing and central hole

69. 1- 2m
• Single entrance wound with irregular margins
• RAT HOLE APPEARANCE

70. > 2 metres
• Pellets begin to spread
• Central hole
• Surrounded by multiple wounds
• Scattered wounds

71. > 4 metres
• Scattered holes
• No central hole
• All of comparable sizes

73. > 5metres
• Wad would produce a typical irregular
wound
• Dispersion of wounds caused by individual
pellets.

74. Exit wounds from a shotgun
• Contact and close range shots  pellets do
make exit wound
• But otherwise they stay within the body
• Thinner body parts like limbs– will have exit
wounds

75. Wounds caused by rifled firearm
• Entrance wound 
• Contact wound – stellate/ cruciate wound
• burning, blackening, tattooing inside the track

77. Close shot
• Burning
• Blackening
• Tattooing around the entrance wound
• Entrance wound usually circular
• edges- inverted

78. • Abrasion collar/ contusion collar
• the abrasion caused around the entry wound
due to the spinning action
• Grease collar/ bullet wipe
• dirt and grease on the bullet

79. NOTE
• Abrasion collar and dirt collar
•  characteristics of an entrance wound

80. Absent abrasion collar
• Entry wound on palms and soles
• Ricochet bullet

81. • Diameter of the bullet 
entrance wound + abrasion collar

82. • Near shot
• Upto 8 cm burning +++
• Upto 15 cm  burning -, tattooing
+,blackening +
• Upto 60 cm  burning -, blackening -,
tattooing +
• Distant shot
• > 60 cm  abrasion collar and grease collar
alone

84. SUMMARY

85. SMOOTH BORE
CONTACT
SHOT
CLOSE NEAR INTERMEDI
ATE
DISTANT RANGE
< 1 metre 1-2
metre
2-4 metre >4 metre > 5 metre
Stellate
wound
Circular wound Irregular
wound
RAT
HOLE
Central hole
large +
satellite
holes
Individual
pellet
holes
Wad
wound +
individual
pellet
wounds
Muzzle
imprint ++
single Single Multiple
wounds
Multiple
Burns +
blackening+
Tattooing +
In the track
Burns + - upto 30 cm
Blackening +- upto 45 cm
Tattooing +-upto 80 cm
Around the wound
------ -------- ---------

86. Rifled firearm
CONTACT SHOT
Point blank
Close shot
(Range of flame)
Near range
(Range of
gunpowder)
Long range
(beyond that
range)
< 8cm <60 cm
Stellate wound
Muzzle imprint
Circular entrance
wound
Abrasion collar
Circular entrance
wound
Abrasion collar
Wound < bullet
Abrasion collar
Burns
Blackening
Tattooing
(in the track)
Burns +
Blackening+
Tattooing+
Burns –
Blackening—
Tattooing ++
Burns--
Blackening--
Tattooing ---

87. Note :
if there is external ricocheting
abrasion collar may be absent
Blackening, burning , tattooing ---

88. ENTRANCE WOUND vs EXIT WOUND
Character Entrance wound Exit wound
Size Smaller than the diameter Larger
edges inverted everted
Abrasion collar
and grease collar
Present Absent
Scorching,
smudging and
tattooing
Present Absent
Bleeding less more
Fat extrusion less more
Cherry red colour May be present absent

89. Yawing/ tembling
• At the last part of the flight,
• Bullet may rotate in a longitudinal axis. Base
comes in front
• Penetrating power is lost
• Irregular lacerated wound is caused

90. • Entrance wound inverted edge
• Exit wound everted edge
• shape may vary considerably

91. Shored exit wound
• If the body is protected at the point of exit
wound
• Wound will be circular
• With abrasion around
• Bullet will be in the vicinity

92. Entrance wound Exit wound
Size- smaller larger
Edges- inverted everted
Burning blackening tattooing + ---
Abrasion collar and grease collar + ----
Bleeding less more
Fat and other tissues – no protrusion protrusion
Metal ring +++ -----

94. Puppe’s rule

95. Tissue quake
• Even the distant organs from the track are
affected

96. Kennedy phenomenon
• Surgically altered entrance or exit wound
• Happened in John. F, Kennedy ‘s assasination

97. Billiard ball Ricochet effect

98. One entrance wound + no exit wound
• Bullet in the body
• Enter the bowel and gets excreted
• May enter trachea and can be spitten out
• May enter the stomach and vomited out
• Deflected throught the same path

99. One entry and multiple exit wounds
• Bullets splitting into two inside the body
• Tandem bullet
• Bullet strikes on the bone comes out with
bone fragment

100. Multiple entry wounds
• Bullet striking and splitting before entering
• Intermediate object secondary missiles+
• Tandem bullets

101. Multiple entrance wounds + single
exit wound
• One may remain and other exit
• One excreted/ coughed

102. Multiple entrance wound and no exit
wound
• Multiple pellets lodged inside

103. Detection of Gunshot residues
• 1. Dermal nitrate/ Paraffin test- non-specific test
• Residues are removed from the suspects hand by
paraffin cast or cotton swab
• Diphenylamine reagent
• Positive test : blue flecks ++

104. • 2. Harrison and Gilroy test
• Qualitative calorimetric test
• Not specific
• But detects antimony, barium and lead
residues

105. • 3. Neutron activation analysis
Detection and measurement of characteristic
isotopes
In a nuclear reactor
Antimony and copper residues from primer

106. • 4. Atomic absorption spectroscopy (AAS)
Or FAAS (Flameless spectrophotometry)
• 5. Scanning electron microscope- energy
dispersive X-ray spectrometry
even minute traces can be detected
• 6. Modified Greiss Test
• Specific For nitrites
• Alpha –naphthol to produce visual display

107. Thank you