Physical Injury

Contusions

blow or squeeze that ruptures small blood vessels without breaking the skin Þ subcutaneous hemorrhage

patterned injuries: appearance of injury indicates weapon used

i.e. cylindrical weapon leave two parallel bruises (width reflects size)

Abrasions

basically scrapes

flaps of skin can indicate direction

drying causes darkening; hemorrhage indicates victim was struggling when abrasion occurred

Lacerations and Incisions

laceration: tearing produced by overstretching skin (hammer)

ragged edges; tissue bridges; abraded margins; undermining; ‘hatband’ distribution in falls
undermining: i.e. on scalp; lifting of skin flap on far edge
deep tissues and organs can sustain lacerations from external blow with no visible evidence

incision: i.e. stabwounds, cuts

clean, straight edges; no tissue bridges; clean margins; no undermining
stab = depth greater than length; incision = depth less than length

wound can be deeper than length of weapon

Langer’s lines (lines of elastic tissue) determine whether wound is open or closed

face and scalp wounds bleed more than those on other parts of body

Blunt Injury

skull fractures: if blunt blow Þ localized indented fracture; fall Þ straight fracture

to abdomen

may have little visible injury; often in child abuse cases

can have laceration, contusion of viscera from crushing against spinal column

rib fractures Þ sharp edges Þ lacerations

fatal blunt trauma without evidence of injury

concussion from blow to head

diffuse axonal injury; does not show up right away

concussion of medula or brain from blow to neck

cardiac concussion Þ arrhythmia

Biting injury

human are characteristic; get 1 to 1 photo and compare to suspect

Gunshots

often misinterpreted (i.e. entry/exit)

contact wound (gun held against skin): sometimes muzzle imprint

tight Þ no fouling

loose Þ fouling (blackened appearance from smoke, heat, etc)

if held against bone (head) gas can get under skin and cause radiating skin splits

close wound: within 6 - 8 inches from body; stippling and fouling

1 to 3 feet: stippling (dots of unburned gunpowder, sand) ; no fouling

bullets, especially rifles, will tumble and cause shock waves that cause extensive tissue laceration

elastic tissue will snap back, inelastic will not (liver)

entrance is usually smaller and more regular than exit wound

not always; also have to look at fouling etc.

Electrocution

injury depends on current and resistance of tissue involved Þ heat

can also disrupt neural regulatory processes; cardiac fibrillation

low voltage (120, 240V): must contact wire; current usually has to pass through heart or brain; ventricular fibrillation Þ death

high voltage: (>1000V) can arc; always have burns

characteristic burns: charred center, pale area, bright red outer margin

most injuries are AC (alternating current)

DC in lightening (less dangerous)

produces arborizing burn (ferning) – they are not invariably fatal

burns: rule of 9’s; adults can sustain 40%, children 20%