Forensic Medicine chapter
SubjectsForensic Medicine
FORENSIC MEDICINE

MECHANICAL INJURIES

141 practice questions · 52 study notes
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Questions

QUESTION 81
Bruising over the shoulder blades suggests which mechanism?
QUESTION 82
Which pigment is associated with the greenish colour of a healing bruise at 5–6 days?
QUESTION 83
What happens to acidic mucopolysaccharides in the connective tissue ground substance of a contusion more than an hour old?
QUESTION 84
At autopsy, what technique is described for demonstrating a scalp contusion?
QUESTION 85
Microscopy of a contusion shows tissue reaction beyond margination and limited emigration of white cells. What does this finding suggest?
QUESTION 86
Why may an antemortem scalp contusion be indistinguishable from postmortem hypostasis in a decomposed body?
QUESTION 87
How are artificial bruises produced to support a false allegation of assault?
QUESTION 88
An incision through a discoloured area reveals firmly clotted blood in surrounding tissues that cannot be removed by a gentle stream of water. What does this finding support?
QUESTION 89
How does colour change progress across a healing bruise?
QUESTION 90
For up to how long after death can great violence produce small bruises in tissues compressed against bone or in hypostatic areas?
QUESTION 91
Which combination favours more rapid healing of a contusion?
QUESTION 92
Why do subconjunctival ecchymoses fail to undergo the usual colour changes of bruises?
QUESTION 93
Which description best distinguishes the usual margins of postmortem bruises from those of antemortem bruises?
QUESTION 94
Which rare complication may follow severe sudden compression of subcutaneous tissue?
QUESTION 95
Which information cannot be determined from a bruise, contributing to its lower medicolegal value compared with an abrasion?
QUESTION 96
An arm has three or four bruises on one side and a single larger bruise on the opposite side. Which mechanism best explains this pattern?
QUESTION 97
How does the depth of a tear caused by an irregular or semisharp object usually vary along its course?
QUESTION 98
Why can temporal arteries bleed freely in scalp lacerations despite the generally limited haemorrhage from lacerated wounds?
QUESTION 99
Which force produces an avulsion laceration by detaching a traumatised surface or viscus from its attachments?
QUESTION 100
When a blunt bottle strikes the skin and produces a laceration, how is the wound edge at the point of impact described?
QUESTION 101
Which mechanism produces a laceration?
QUESTION 102
Lacerated wounds are found over the parietal prominence, ear and lower jaw on one side of the head. What can be concluded about the minimum number of blunt blows required to produce these wounds?
QUESTION 103
Why are the edges of a typical lacerated wound irregular and rough?
QUESTION 104
Blunt trauma produces extensive bruising together with laceration of deeper tissues. What is this injury termed?
QUESTION 105
What does equal undermining on all sides of a lacerated wound indicate about the impact?
QUESTION 106
A severe skull fracture is found without an external scalp laceration. Which characteristic of the striking instrument can explain this combination?
QUESTION 107
Why do tissue bridges remain across the bottom of a lacerated wound?
QUESTION 108
A head injury has a large flap of tissue torn away, exposing the underlying skull. Which type of force can produce this finding?
QUESTION 109
Which combination characterizes a split laceration?
QUESTION 110
Why can a blunt-force wound over the shin resemble an incised wound?
QUESTION 111
A pedestrian struck by a motor vehicle has apparently uninjured skin over the back of the thigh, but the underlying soft tissue is separated from fascia, creating a blood-filled pocket. Which force explains this injury?
QUESTION 112
What are 'swallow tails' in a lacerated wound?
QUESTION 113
Why may temporal arteries bleed freely following a laceration?
QUESTION 114
Which scalp finding is described following a fall on the head?
QUESTION 115
Which sequence explains the greater mass of scar tissue in healing by second intention?
QUESTION 116
Under which circumstance may a straight-bladed weapon produce a crescentic incised wound?
QUESTION 117
How does the orientation of divided underlying muscle fibres affect gaping of an incised wound?
QUESTION 118
Where are hesitation marks typically found in relation to an incised wound?
QUESTION 119
Crushing of subcutaneous tissue associated with a laceration may produce which embolic complication?
QUESTION 120
An incised wound begins as several skin cuts that merge into one at its end. Which action of the weapon produces this pattern?
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Study notes

Definitions and classification of injuries
Injuries can be described medically by the tissue damage and causative agent, legally by severity categories, and medicolegally by the circumstances of occurrence. →
Mechanical injury: energy transfer and tissue deformation
Mechanical impact transfers energy to tissues. The resulting injury depends on how tissues move, deform and resist strain. →
Factors determining wound severity: contact area, energy and immobilization
The nature and extent of a wound depend on the striking object, the energy delivered and the conditions under which that energy is discharged. →
Mechanical injury: responses of skin, soft tissues, bone and body fluids
Different tissues respond differently to a blow because of their mechanical properties. Movement and the duration of energy discharge also influence injury. →
Wound severity, forensic interpretation and the definition of abrasion
Injury severity depends on tissue properties and the circumstances of impact. These variations limit precise forensic estimates of the force used. →
Abrasions: mechanism, depth, scab formation and scratches
Abrasions result from pressure and movement at the skin surface. Their depth and pattern reflect the abrading surface and the manner of contact. →
Fingernail mark distortion, grazes and friction burns
Movement across the skin produces characteristic abrasion patterns. Skin recoil can alter nail marks, while grazing and friction injuries have distinct surface appearances. →
Pressure, impact and patterned abrasions
Abrasion morphology reflects how an object contacts the skin and may preserve features of the causative object. →
Patterned abrasions and the sequence of abrasion healing
Surface patterns can indicate the contact object, while gross and microscopic healing changes help assess the approximate age of an abrasion. Exact age cannot be determined. →
Recognition and limitations of postmortem abrasion assessment
The timing of an abrasion relative to death can be difficult to establish, and drying or immersion can alter its visibility and appearance. →
Interpretation of abrasion distribution and recognition of ant erosions
The location and appearance of abrasions can help reconstruct a fall or assault, connect injuries with objects or scenes, and distinguish injury mimics. →
Contusions: mechanism, location and characteristic features
Contusions are blood effusions caused by blunt trauma. The passage also describes skin changes that may resemble abrasions. →
Bruise appearance and factors affecting size and visibility
Bruise size and appearance depend on tissue structure, force, age and other circumstances, so the visible mark does not reflect force alone. →
Sex, body habitus and visibility of bruising
Susceptibility to bruising and its visible appearance vary with tissue characteristics, skin pigmentation and methods of examination. →
Disease-related bruising and migration of extravasated blood
Disease can increase bruising after minimal force, and blood tracking through tissues can produce visible bruises away from the site of injury. →
Patterned contusions and the effect of impact
The shape of a contusion may preserve information about the object that caused it. →
Bruise shape after impact by solid objects and sticks
Bruise shape depends on the object and which part of it strikes the body. →
Patterned contusions and delayed bruising
Bruise patterns can reflect the impacting surface or clothing, while deeper bruises may become visible only after a delay. →
Mechanisms and identifying patterns of weapon-related bruises
Different objects produce characteristic contusion patterns through compression, stretching and displacement of blood. →
Postmortem changes in bruises and consequences of organ contusions
Bruise appearance can change after death, and deep contusions can cause severe functional injury despite limited external evidence. →
Bruise healing and the sequence of colour changes
Bruises heal through destruction and removal of extravasated blood. Their colour reflects blood breakdown, but the rate of change varies. →
Limitations of bruise dating and evidence of antemortem injury
Colour and microscopic findings can help assess bruises, but neither permits confident determination of their exact age. →
Production of small bruises shortly after death
Arrest of circulation limits appreciable bruising after death, although force can still produce small bruises under particular conditions. →
Autopsy demonstration of bruises and effects of decomposition
Bruises may require dissection for detection, while decomposition can obscure the distinction between trauma and postmortem blood pooling. →
Bruise distribution and differentiation from hypostasis
The distribution of bruises may suggest how force was applied. Incision findings and tissue appearance help distinguish bruising from hypostasis. →
Medicolegal limitations, complications and circumstances of bruising
Bruises have limitations in reconstructing injury mechanisms and may cause serious complications. Irritant-induced skin injuries can also simulate bruising. →
Lacerations: definition and associated injury observations
Lacerations are blunt-force tears or splits involving skin, mucous membranes, muscle or internal organs. →
Lacerations: formation, wound margins and descriptive terms
Blunt impact displaces local tissue, creating traction that tears it. The resulting appearance reflects crushing, stretching and rubbing by the striking object. →
Split, stretch and avulsion lacerations
Different patterns of tissue compression, stretching and shearing produce distinct forms of laceration. →
Avulsion, tears and concealed blunt-force injury
Lacerations may involve deep tissues or internal organs despite limited external skin injury. →
Laceration edges and swallow tails
Blunt impact can produce different appearances at opposing wound edges, together with characteristic tears at the wound ends. →
Lacerations: directional signs, tissue bridges, bleeding and vitality
Wound structure can help interpret the direction of blunt impact, while healing and vital reactions help assess timing and antemortem occurrence. →
Lacerations: complications, circumstances and associated blunt injuries
Lacerations can cause serious complications, while their pattern and associated injuries may help explain how they were produced. →
Kicking injuries and the mechanism and margins of incised wounds
This passage describes injuries from kicking and stamping, then defines incised wounds and explains their production, margins and width. →
Incised wounds: length, interrupted cuts, shape and gaping
The dimensions and appearance of an incised wound depend on movement of the cutting edge, skin folding and the orientation of underlying muscle fibres. →
Incised wounds: surface effects, bleeding and direction of cutting
Wound shape is influenced by the skin surface and blade orientation, while differences in depth and margin configuration help indicate the direction of cutting. →
Incised wound healing, second intention and wounds caused by glass
The passage gives a sequence for uncomplicated incised wound healing, describes the greater scarring of second-intention healing, and explains why glass wounds can resemble sharp-force injuries. →
Self-inflicted incised wounds and hesitation marks
Patterns, accessible sites and tentative cuts help characterize self-inflicted wounds, although a suicidal fatal incision can be large and gaping. →
Suicidal and homicidal cut-throat wounds
The readable comparison rows describe differences in wound level, hesitation cuts, tailing, weapon recovery and clothing damage. →
Patterns and circumstances of incised wounds
Incised-wound location, direction and associated circumstances help distinguish suicidal, homicidal and accidental injuries. →
Chop wounds and limitations of wound interpretation
Chop wounds result from heavy sharp-edged weapons. Their depth and bone defects can indicate how the blow was delivered. →
Chop-injury circumstances and stab-wound characteristics
The passage completes the discussion of chop injuries and introduces the mechanism, types and margins of stab wounds. →
Stab-wound abrasions and measurement of wound length
The position of a hilt abrasion can reflect the angle of stabbing, while skin stretching and weapon movement affect measured wound length. →
Stab wounds: visceral position, penetration and tissue resistance
Assessment of a stab wound must account for changes in body position after death, the properties of the knife and resistance offered by tissues. →
Stab wounds: penetration, track examination and skin shape
The depth, track and external appearance of a stab wound depend on the weapon, clothing, skin and movements involved. →
Defence wounds and assessment of the circumstances of injury
The circumstances of injury are assessed from wound features, the suspected weapon and the scene. Defence wounds reflect the victim's immediate, instinctive attempts at protection. →
Sharp-weapon defence wounds
The distribution and appearance of defensive cuts vary with the weapon and the victim's attempt to grasp or ward off it. →
Offensive hand injuries and fabricated wounds
Hand injuries may help reconstruct an assault. Fabricated wounds are assessed through their morphology, distribution, clothing findings and the stated history. →
Shotgun wounds at a short range of 1–2 metres
At this range, the shot enters as a single mass and produces a characteristic entrance wound without burning, blackening or tattooing. →
Back spatter in firearm injuries
In contact shots, material drawn back into the firearm barrel is termed back spatter. →
Firearm wounds: clothing, muzzle gases and soot distribution
Muzzle gases and smoke produce characteristic findings in clothing and within firearm wounds. →
Bullet wounds: skull bevelling, shot sequence and direction
Skull defects, fracture-line relationships and the abrasion collar provide evidence about bullet passage and the sequence or direction of firing. →
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