BFI Flashcards
Define wound
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
Define injury
Disruption of continuity of tissues produced by
- physical force
- heat/cold
- chemicals
- electricity
- radiation
Define lesion
Any area of injury, disease or local degeneration in a tissue causing a change in its function or structure
Define blunt force injury
Bodily damage resulting from forceful contact between the body and a blunt object
- involves movement and impact with the resulting transfer of kinetic energy
Types of mechanical force
Impact Angulation Compression Traction Torsion Shearing Acceleration/deceleration
Types of blunt force injury
Abrasions
Bruises
Lacerations
Types of trauma
Mechanical force - blunt force - sharp force - explosive /firearm Heat/cold Electrical current Atmospheric pressure Radiation - particulate - wave Chemical reaction
Factors affecting injury
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
Kinetic energy is imparted to the tissues when
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
Vehicle Crash Energy =
Energy=(mph^2 ×0.034)/(stopping distance)
Classification of mechanical injuries
Blunt force - abrasions - bruises - lacerations Sharp force - incisions - stabs Firearm/explosive
Features of describing injureis
Observation Documentation - site - precise location - type of injury - shape - size - associated features - clinical effects
Define haemorrhage
Escape of blood from any part of vascular system
- heart
- arteries
- veins
Types of haemorrhage
External - onto body surface
Internal - into body cavity
Bruising - haemorrhage into tissues
Define bruising
Escape of blood from ruptured small vessels into subcutaneous fat or dermis
Occurs in life
Due to blunt force trauma
Mechanism of bruising
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
Define haematoma
Swollen bruise
Blood collects in discrete tumour like pool
Difficulties with bruising
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
Distinctive bruise shapes
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
Factors affecting site of bruising
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
Factors affecting severity of bruise
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
Age of bruises
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
Classic patterns of bruising
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
Define lividity
Blood settling post mortem
Occurs with gravity
Define abrasion
Superficial/partial thickness skin injury
Crushing or scraping of epidermis and partial thickness of dermis
Mechanisms of abrasion
Crushing - imprint - by vertical force Scraping - by tangential force - graze over broad surface - scratch by fine point
Features of abrasions
Clinically trivial
Bleeding is slight
Heal quickly
Leave no scar
Features of imprint abrasion
Compression of epidermis
No bleeding as not deep enough to reach blood vessels
Causes of imprint abrasions
Footwear Tyre impressions Clothing weave Ligature weave Seatbelt Vehicle parts Weapon Hilt of knife
Mechanism of scraping abrasions
Grazing along skin surface
Pushes epidermis up into tags
Deroofing of dermal capillary - pinpoint of blood appearing
Forensic importance of abrasions
Always occur at site of impact
Often reflect pattern of causal object/surface
Often indicate direction of impact
Possible trace evidence transfer
Situations where bite marks occur
- pets
- siblings
- self-inflicted
- sports
- assault - sexual assault and child abuse
Features of bite mark
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
Define laceration
Full thickness tear in tissue
Due to blunt force trauma
Force types of lacerations
Crushing/splitting - occurs over bone Stretching/tearing - leaves intact some strands of stronger subcut tissue which straddle the wound - skin stretched beyond elastic limit
Features of lacerations
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
Clinical significance of lacerations
External haemorrhage often slight - skull is exception Often requires suturing FB/wound infection common Heals by scaring Often confused with incisions
Laceration vs incision
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
