BFI

Question 1

Define wound

Answer 1

Disruption of continuity of tissues produced by external mechanical force
Legally - breach of the full thickness of the skin or lining of lip - excludes bruising, abrasion and fracture

Question 2

Define injury

Answer 2

Disruption of continuity of tissues produced by

• physical force
• heat/cold
• chemicals
• electricity
• radiation

Question 3

Define lesion

Answer 3

Any area of injury, disease or local degeneration in a tissue causing a change in its function or structure

Question 4

Define blunt force injury

Answer 4

Bodily damage resulting from forceful contact between the body and a blunt object
- involves movement and impact with the resulting transfer of kinetic energy

Question 5

Types of mechanical force

Answer 5

Impact
Angulation
Compression
Traction
Torsion
Shearing
Acceleration/deceleration

Question 6

Types of blunt force injury

Answer 6

Abrasions
Bruises
Lacerations

Question 7

Types of trauma

Answer 7

Mechanical force
- blunt force
- sharp force
- explosive /firearm
Heat/cold
Electrical current
Atmospheric pressure
Radiation
- particulate
- wave
Chemical reaction

Question 8

Factors affecting injury

Answer 8

Physical
- degree of force applied
- area of application of force
- duration of application
- direction of application
- tissue properties - viscosity, plasticity, elasticity
Biological
- mobility of body part - fixed body part has complete energy transfer
- anticipation and coordination - allows for bracing and force absorption
- biomechanical properties of tissue - skin is elastic and resists stretching

Question 9

Kinetic energy is imparted to the tissues when

Answer 9

A moving object strikes body
Or moving body strikes stationary object
	- E= 1/2  m.v^2
E = kinetic energy
M = mass of object
V = velocity of object

Question 10

Vehicle Crash Energy =

Answer 10

Energy=(mph^2 ×0.034)/(stopping distance)

Question 11

Classification of mechanical injuries

Answer 11

Blunt force
- abrasions
- bruises
- lacerations
Sharp force
- incisions
- stabs
Firearm/explosive

Question 12

Features of describing injureis

Answer 12

Observation
Documentation
- site
- precise location
- type of injury
- shape
- size
- associated features
- clinical effects

Question 13

Define haemorrhage

Answer 13

Escape of blood from any part of vascular system

• heart
• arteries
• veins

Question 14

Types of haemorrhage

Answer 14

External - onto body surface
Internal - into body cavity
Bruising - haemorrhage into tissues

Question 15

Define bruising

Answer 15

Escape of blood from ruptured small vessels into subcutaneous fat or dermis
Occurs in life
Due to blunt force trauma

Question 16

Mechanism of bruising

Answer 16

Blood vessels more vulnerable to stretching and rupture that overlying skin - rupture of venules/arterioles
Haemorrhage seen as discolouration through intact overlying skin - dark skin may mask

Question 17

Define haematoma

Answer 17

Swollen bruise

Blood collects in discrete tumour like pool

Question 18

Difficulties with bruising

Answer 18

Site of bruise not always site of impact - blood can track (leak out)
Appearance may be delayed
Shape rarely reflects shape of causal object
Size rarely reflects severity of impact
Accurate ageing is difficult

Question 19

Distinctive bruise shapes

Answer 19

Intradermal bruise - footwear
- haemorrhage in dermis but not subcutaneous fat
- tread remains visible
- negative of shoe tread - bruising occurs in areas next to tread due to stretch
Seat belt bruise
- diagonal and horizontal bruise
Tramline
- rod-shaped instrument
- central compression spares tissue
Doughnut
- circular impact

Question 20

Factors affecting site of bruising

Answer 20

Depends on site and depth of blood leakage
Tracks along planes of least resistance
- natural or traumatic
Gravity and muscle movement
Delayed appearance on skin surface

Question 21

Factors affecting severity of bruise

Answer 21

Degree of force applied
Site of impact
- loose fatty tissue bruise more readily - face, thighs
Age of victim
- very young very old have poorly developed/degeneration of connective tissue
Sex
- females bruise more readily - tend to have a greater thickness of subcut fat
Obesity
- greater thickness of subcut fat
Natural disease
- haemophilia
- thrombocytopenia
Alcoholics
- increased falls risk
- impaired liver function - reduced clotting proteins

Question 22

Age of bruises

Answer 22

Dark red = immediate
- oxyhaemoglobin
Dusky purpled = minutes
- deoxyHb
Brown - 1-3 days
Green = 4-5 days
- biliverdin
Yellow = 7-10 days
- bilirubin
Disappears = 7-14 days
Great variance in and between people

Question 23

Classic patterns of bruising

Answer 23

Punching and kicking - face and ears
Patterned intradermal bruise from tread - stamping/run over
Strangulation - upper neck
Forceful restraint - limbs
Counter pressure (pushed up against wall/floor) - back
Repeated assaults - various ages
Resuscitation - face, neck and chest
Children often have bruises on skins from playing - should be of various ages

Question 24

Define lividity

Answer 24

Blood settling post mortem

Occurs with gravity

Question 25

Define abrasion

Answer 25

Superficial/partial thickness skin injury

Crushing or scraping of epidermis and partial thickness of dermis

Question 26

Mechanisms of abrasion

Answer 26

Crushing
- imprint
- by vertical force
Scraping 
- by tangential force
- graze over broad surface
- scratch by fine point

Question 27

Features of abrasions

Answer 27

Clinically trivial
Bleeding is slight
Heal quickly
Leave no scar

Question 28

Features of imprint abrasion

Answer 28

Compression of epidermis

No bleeding as not deep enough to reach blood vessels

Question 29

Causes of imprint abrasions

Answer 29

Footwear
Tyre impressions
Clothing weave
Ligature weave
Seatbelt
Vehicle parts
Weapon
Hilt of knife

Question 30

Mechanism of scraping abrasions

Answer 30

Grazing along skin surface
Pushes epidermis up into tags
Deroofing of dermal capillary - pinpoint of blood appearing

Question 31

Forensic importance of abrasions

Answer 31

Always occur at site of impact
Often reflect pattern of causal object/surface
Often indicate direction of impact
Possible trace evidence transfer

Question 32

Situations where bite marks occur

Answer 32

• pets
• siblings
• self-inflicted
• sports
• assault - sexual assault and child abuse

Question 33

Features of bite mark

Answer 33

Combination of abrasion, bruising and laceration
Animal bites are deeply arched and lacerations present
Human bite is circular or shallow oval
Injury due to
- tissue drawn into mouth
- abrasion/bruising from teeth
- suction bruise centrally

Question 34

Define laceration

Answer 34

Full thickness tear in tissue

Due to blunt force trauma

Question 35

Force types of lacerations

Answer 35

Crushing/splitting
- occurs over bone
Stretching/tearing
- leaves intact some strands of stronger subcut tissue which straddle the wound
- skin stretched beyond elastic limit

Question 36

Features of lacerations

Answer 36

Due to blunt force Trauma
Ragged edges
Tissue bridges in base
Associated bruising and abrasion
Do not usually indicate shape of causal object or surface
Bleeding is less than expected
- due to spasm/retraction of vessels
May harbour trace evidence

Question 37

Clinical significance of lacerations

Answer 37

External haemorrhage often slight
- skull is exception
Often requires suturing
FB/wound infection common
Heals by scaring
Often confused with incisions

Question 38

Laceration vs incision

Answer 38

Laceration
- due to blunt force
- tissue bridges
- bruising in base
- marginal abrasion
- slight bleeding 
- trace evidence
Incision
- due to sharp edge
- no tissue bridge
- no bruising
- no abrasion
- profuse bleeding
- no trace evidence