Blunt Force Trauma

Characteristics of Instruments Size –length and width Shape –cross-sectional outline round -- more fx lines angular -- fewer fx lines, distinct edges –patterned injuries Weight –heavy or light

Effects of BFT on bone Inbending at the site of force Outbending around the site of force LeFort fractures Ring fractures

Sharp Force Trauma

Caused by an implement with an edge or point Usually results from compression or shearing applied over a narrow focus Complete discontinuities result from chopping instruments while infractions from cutting instruments.

Effects of Sharp Instruments PunctureIncisionCleft/notchStriationsWastage

Punctures Caused by pointed instrument directed toward a bone surface –Indentation at point of contact (cone-shaped) –Depth of wound depends on instrument and causative force

Incisions Sharp forces drawn across cortical surface –Thin lines or V-shaped indents –Fracture lines are rare –Length, width, depth of wound depends on size of instrument, amt. of energy and dimensions of bone impacted

Clefts Caused by vertical forces applied by heavy instruments with long, sharp edges –V-shaped notch –May be accompanied by radiating fractures –Depth depends on force applied

Knives Wound is generally small, clean and sharp edged - variation depends on size, type, weight and sharpness of the knife (e.g. paring knife v. serrated bread knife) Knife wounds are characterized by straight lines - straight lines are seldom found in nature

Anatomy of a Knife BackSpineEdgePointRicassoCrossguardGripHandle

Machetes Wound is generally long, deep and sharp- edged Machetes can penetrate or decapitate

Other Cutting Instruments Wound is related to the type of tool used (ice pick, hammer, screwdriver, pliers) Tool may have individualized characteristics that may tie it to the wound produced

Other tools, cont. NEVER compromise the integrity of the evidence by trying to fit the object into the hole it produced. One may only say that a wound is consistent with a particular instrument (unless you have an individualizing element such as a broken tip that matches the suggested tool)

Wound Analysis Description of wound Instrument characteristics –type cutting, stabbing, chopping –size blade length, width, surface contour, sharpness Direction of force Number of traumatic events

Miscellaneous Strangulation –hanging, ligature, manual strangulation Fire Chemical Trauma