ANTH 245 1st Edition Lecture 10Outline of Last Lecture - Description of film Forensics on Trial- Madrid Bomber- Syracuse Farm House Fire- Nicole Brown Simpson CaseOutline of Current Lecture- Principals of BFT that govern damage- BFT to soft tissue- Bone Biomechanics - Stress-Strain CurveCurrent LectureBlunt Force Trauma InterpretationBlunt Force Trauma:- Injury caused by a blunt object or collision with a blunt surface- Example: being hit by a car- Example: falling off a building and hitting the pavement - Transfer of kinetic energy between an object and a body- "Energy in motion"Principles of BFT that Govern damage- Amount of force applied- Velocity of force applied- Velocity of strike- Area of distribution of strike on body- Nature of the weapon; if it can deform or not- If it can deform, some energy would be absorbed by the weapon- Nature of body surface struck Some terms:Ante mortem - Before deathPeri mortem - Around the time of deathBFT to soft tissueThree types:- Contusions (bruise)o Bruises or hematomaso Rupture of blood vessels with blood loss into surrounding tissueo The skin is unbrokeno Hard to tell which contusions are older o Rarely occurs postmortemo Patterned and un-patterned o Can have a contusion to your organs- Abrasions (scrape)o Superficial removal of epidermiso Scrape caused by rubbing against blunt objecto Often get contusions and abrasions togethero Can tell age based on degree of healingo Two types: Scrape - blunt object scraped off layers of skin E.g. road rash Impact Abrasion: Crushing by a blunt object Can be patterned - imprint of the object - Lacerations (tearing)o Tissue tear due to crushing or shearing force o Wound is longer than it is deepo Tissue bridging: little lines of connective tissue hold skin together across the lacerationo Typically have abraised, irregular marginso Might have particles from object in woundo Morphology (shape) may not be representative of the objecto Perpendicular (crushing) blows E.g. from hammer, fall to the ground in boxingo Glancing blows (at an angle) may create gaping woundso Sometimes mimic sharp force traumao Avulsion skin and soft tissue ripped off the boneBFT- All types of BFT can occur on one individual or in one wound- Soft tissue and bone often both affected- Defense wounds: BFT occurs on the back of the arms and hands to ward off blows- Parry fractures - Ulna (one of two bones in the forearm)Minimum number of blows/impacts (never assess for a maximum)Bone Biomechanics- Bone is viscoelastic- Both rigid and bendable at the same time- Minerals in bone make it rigid, collagen makes it bendable- Under small loads bone will deform- Deformation: how fast the load is applied; for how long; properties of the bone- Larger bones are more resistant to fracture than smaller bonesStress-Strain Curve- Bone reacts to a slow-loading stress (trauma) by straining (bending)- Bone bends before it breaks- Elastic: it deforms but bounces back- Plastic - deformation so great it can't bounce back- Bone is permanently deformed- If stress continues, bone will
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