MECHANICAL 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 impact transfers energy to tissues. The resulting injury depends on how tissues move, deform and resist strain. →

The nature and extent of a wound depend on the striking object, the energy delivered and the conditions under which that energy is discharged. →

Different tissues respond differently to a blow because of their mechanical properties. Movement and the duration of energy discharge also influence injury. →

Injury severity depends on tissue properties and the circumstances of impact. These variations limit precise forensic estimates of the force used. →

Abrasions result from pressure and movement at the skin surface. Their depth and pattern reflect the abrading surface and the manner of contact. →

Movement across the skin produces characteristic abrasion patterns. Skin recoil can alter nail marks, while grazing and friction injuries have distinct surface appearances. →

Abrasion morphology reflects how an object contacts the skin and may preserve features of the causative object. →

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. →

The timing of an abrasion relative to death can be difficult to establish, and drying or immersion can alter its visibility and appearance. →

The location and appearance of abrasions can help reconstruct a fall or assault, connect injuries with objects or scenes, and distinguish injury mimics. →

Contusions are blood effusions caused by blunt trauma. The passage also describes skin changes that may resemble abrasions. →

Bruise size and appearance depend on tissue structure, force, age and other circumstances, so the visible mark does not reflect force alone. →

Susceptibility to bruising and its visible appearance vary with tissue characteristics, skin pigmentation and methods of examination. →

Disease can increase bruising after minimal force, and blood tracking through tissues can produce visible bruises away from the site of injury. →

The shape of a contusion may preserve information about the object that caused it. →

Bruise shape depends on the object and which part of it strikes the body. →

Bruise patterns can reflect the impacting surface or clothing, while deeper bruises may become visible only after a delay. →

Different objects produce characteristic contusion patterns through compression, stretching and displacement of blood. →

Bruise appearance can change after death, and deep contusions can cause severe functional injury despite limited external evidence. →

Bruises heal through destruction and removal of extravasated blood. Their colour reflects blood breakdown, but the rate of change varies. →

Colour and microscopic findings can help assess bruises, but neither permits confident determination of their exact age. →

Arrest of circulation limits appreciable bruising after death, although force can still produce small bruises under particular conditions. →

Bruises may require dissection for detection, while decomposition can obscure the distinction between trauma and postmortem blood pooling. →

The distribution of bruises may suggest how force was applied. Incision findings and tissue appearance help distinguish bruising from hypostasis. →

Bruises have limitations in reconstructing injury mechanisms and may cause serious complications. Irritant-induced skin injuries can also simulate bruising. →

Lacerations are blunt-force tears or splits involving skin, mucous membranes, muscle or internal organs. →

Blunt impact displaces local tissue, creating traction that tears it. The resulting appearance reflects crushing, stretching and rubbing by the striking object. →

Different patterns of tissue compression, stretching and shearing produce distinct forms of laceration. →

Lacerations may involve deep tissues or internal organs despite limited external skin injury. →

Blunt impact can produce different appearances at opposing wound edges, together with characteristic tears at the wound ends. →

Wound structure can help interpret the direction of blunt impact, while healing and vital reactions help assess timing and antemortem occurrence. →

Lacerations can cause serious complications, while their pattern and associated injuries may help explain how they were produced. →

This passage describes injuries from kicking and stamping, then defines incised wounds and explains their production, margins and width. →

The dimensions and appearance of an incised wound depend on movement of the cutting edge, skin folding and the orientation of underlying muscle fibres. →

Wound shape is influenced by the skin surface and blade orientation, while differences in depth and margin configuration help indicate the direction of cutting. →

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. →

Patterns, accessible sites and tentative cuts help characterize self-inflicted wounds, although a suicidal fatal incision can be large and gaping. →

The readable comparison rows describe differences in wound level, hesitation cuts, tailing, weapon recovery and clothing damage. →

Incised-wound location, direction and associated circumstances help distinguish suicidal, homicidal and accidental injuries. →

Chop wounds result from heavy sharp-edged weapons. Their depth and bone defects can indicate how the blow was delivered. →

The passage completes the discussion of chop injuries and introduces the mechanism, types and margins of stab wounds. →

The position of a hilt abrasion can reflect the angle of stabbing, while skin stretching and weapon movement affect measured wound length. →

Assessment of a stab wound must account for changes in body position after death, the properties of the knife and resistance offered by tissues. →

The depth, track and external appearance of a stab wound depend on the weapon, clothing, skin and movements involved. →

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. →

The distribution and appearance of defensive cuts vary with the weapon and the victim's attempt to grasp or ward off it. →

Hand injuries may help reconstruct an assault. Fabricated wounds are assessed through their morphology, distribution, clothing findings and the stated history. →

At this range, the shot enters as a single mass and produces a characteristic entrance wound without burning, blackening or tattooing. →

In contact shots, material drawn back into the firearm barrel is termed back spatter. →

Muzzle gases and smoke produce characteristic findings in clothing and within firearm wounds. →

Skull defects, fracture-line relationships and the abrasion collar provide evidence about bullet passage and the sequence or direction of firing. →