Blunt force - tools

• Tool Type

  •Weapons may have their own unique characteristics leaving individuating tool marks on soft and hard tissues

  •Matching ‘exact’ tool type can be extremely difficult

  •Need to take into account contact surface area of the tool, primary  or secondary surfaces, edges, and the effects of overlying soft  tissues

  •Depending on degree of plastic deformation it may be impossible to  match – so may be attributed to class – ‘consistent with’ damage
• Tool Characteristics

  •Size

  –Length and width of object

  –Unless long axis of object is imprinted in bone, the size cannot be  estimated objectively

  –Difficult to differentiate blow vs collision (e.g fall)

  •Context in which remains are found is important

  –Small objects require less force to cause fracture than wide  instruments
• Tool Characteristics

  •Shape

  –Relates to cross-sectional outline and longitudinal shape

  –Round or angular cross-sectional shapes most common

  •Round (eg bottle or baseball bat)

  •Angular (eg batton or crowbar)

  –more likely to inflict an injury with distinct, incisive edges with fewer fracture  lines

  –Leave impression behind

  –Rarely patterned injuries can occur that specifically identify the  causative injury

  –Most easily observed on soft tissue

  –Rarely observed on bone

  •Cranial vault most likely to exhibit patterned injury
• Tool Characteristics

  •Weight

  –Can only be estimated and differentiated  as heavy or light

  •Light objects cause smaller injuries

  •Heavy injuries cause more severe injuries

  –All depends on force used

  •A light and heavy object used at same force  will result in small and severe injuries  respectively

  •A light object used with high force and a  heavy object used with low force may cause  similar injuries.

  –Weight is not applicable in collision or fall  injuries
• Description of Trauma

  •Document:

  –Bone affected

  –Location of injury using appropriate anatomical terminology

  –Side

  –Surface

  –Type of fractures present

  –Description of each injury in isolation if multiple present

  •Include details on amount of displacement, number of displacements,  presence and type of fracture lines, wastage, plastic deformation
• Wound Analysis

  •Description of Wound

  •Estimation of Size

  •Estimation of Shape

  •Estimation of Direction

  •Estimation of Energy

  •Estimation of Number

  •Estimation of Sequence
• Sequence and Order of Blows

  •Sequencing damage relies on two primary factors:

  –Intersection of fractures

  •Dissipation of energy between fractures and sutures can give the  order of fracture propagation

  •As integrity is reduced the energy in subsequent blows is  insufficient to propagate into already fractured regions or plates of  bone

  •More recent fractures generally cannot ‘jump’ existing factures  (including sutures)as they lack energy to do so

  –Overlap of applied trauma

  •Wounds generally need to be contiguous rather than isolated in  order to assess order
• What can trauma tell us?

  When: Anti, Peri, Post Mortem?

  What: What object caused the injury?

  How many: How many blows there were?

  Sequence: What order did they happen in?

  Where: Where on the body did they occur?

  How: How were they inflicted?

  Who: Who inflicted them?

  Why: Why were they inflicted?