Forensic Aspects of Trauma 1

Question 1

what is the definition of an injury?

Answer 1

‘physical harm or damage to someone’s body caused by an accident or an attack’

‘Damage to any part of the body due to the application of mechanical force’

Question 2

mechanism of injury - what is the human body constantly subjcted to?

Answer 2

Human body is constantly subjected to mechanical forces – from unceasing gravitation forces to forceful impacts of for example a sporting activity

Question 3

mechanism of injury - what laws do the intensity of force obey?

Answer 3

Intensity of the force obeys the usual laws of physics:

• Force varies directly with mass of the ‘weapon’ and directly with square of velocity of impact
• Kinetic energy = ½ mass x velocity²
• 1kg brick held against the scalp causes no injury but same brick thrown at the head at 10m/s may smash the skull

Question 4

mechianism of injuty - another important factor to consider is the area over which the force acts, what are some examples?

Answer 4

• Plank of wood - damage to tissue is far greater if narrow edge is used rather than wide edge - The force derived from the same mass and velocity is applied over a smaller area, thus delivering a greater impact to any given unit of tissue
• Tip of knife vs cricket bat – kinetic energy of moving knife concentrated into tiny area of tip of blade; same energy delivered over a large surface area such as cricket bat may not even leave a bruise
• Seatbelts - stretching of seatbelt fabric extends time of energy exchange and considerable area of seatbelt surface is preferable to alternative of transferring all kinetic energy via a few cm² of the forehead against the windscreen

Question 5

mechanism of injury - excessive mechanical force can cause what?

Answer 5

• Compression
• Traction
• Torsion
• Tangential (shearing)

Question 6

mechanism of injury - Resultant damage depends on type of _________ insult AND _____ of target tissue

Answer 6

Resultant damage depends on type of mechanical insult AND nature of target tissue

Question 7

what are the different classifications of injury?

Answer 7

apperance or method of causation

manner of causation

nature of injury

Question 8

Classification of Injury - what are examples of different appearance or method of causation?

Answer 8

Abrasion, contusion, laceration, incised wounds, gunshot wounds, burns

Question 9

Classification of Injury - what are examples of different manners of causaion?

Answer 9

Suicidal, accidental, homicidal

Question 10

Classification of Injury - what are different examples of the nature of the injury?

Answer 10

Blunt force, sharp force, explosive

Question 11

what is the anatomy of the skin like?

Answer 11

Question 12

what causes bllunt force injuries?

Answer 12

Caused by impact with blunt object – ground, fist, foot, weapon

Question 13

what are different blunt force injuries?

what are the kinds of injuries you get with impact with a blunt object?

Answer 13

• Contusions (bruises) - Burst blood vessels in skin
• Abrasions (graze, scratch) - Scraping of skin surface, epidermis being scrapped off by the impact of the blunt object, Abrasions don’t normally bleed very much
• Lacerations (cut, tear) - Tear/split of skin due to crushing, bleed more, more ragged than incised wounds (which is clean cut with not much associated brusing)

Question 14

what are Contusions?

Answer 14

Bruises: burst blood vessels in skin

more purple = fresher

Question 15

what types of Patterned Bruises is there?

(useful as sometimes they are particular for certain impacts/wepons)

Answer 15

Tramline bruises e.g. broom handle

Finger tip bruising (pictures on the question side showing this), shows grip marks

Other patterns

Question 16

what are factors that affect prominence?

Answer 16

• Skin pigmentation - in lighter skin bruises are easier to see
• Depth and location – occur more readily over loose skin – eyebrow, scrotum
• Fat - ↑ subcut fat = bruise more easily
• Age - Children – skin loose and delicate, Elderly - blood vessels of skin poorly supported
• Resilient areas – buttocks, abdomen – bruise less easily with given impact than areas with underlying bone which acts as an anvil with skin between bone and inflicting object
• Coagulative disorders – thrombocytopenia, Von Willebrand’s disease, haemophilia, liver disease (alcoholics), bone marrow disease

Question 17

what are Abrasions?

Answer 17

Graze, scratch - scraping of skin surface

tags give indication of direction

Question 18

what may Patterned Abrasions look like?

Answer 18

Question 19

what are lacerations?

(black arrows pointing to tissue bridges - these show it is a laceration and a blunt force trauma)

Answer 19

Cut/tear/split of skin due to crushing

typically in areas where skin or soft tissues overlays bone

ragged edge

Question 20

how are sharp force injuries caused?

Answer 20

Injury caused by any weapon with sharp cutting edge

superficial or penetrating

Question 21

what are 2 kinds of sharp force injuries?

Answer 21

incised wounds and stab wounds

Question 22

what are incised wounds?

Answer 22

• Superficial sharp force injury caused by slashing motion
• Longer on the skin surface than it is deep

Question 23

what are stab wounds?

Answer 23

• Penetrating injury resulting from thrusting motion
• Wound depth greater than length on the surface

Question 24

do you get “Patterned” Stab Wounds?

Answer 24

yes