Forces generated in stabbing attacks: an evaluation of the utility of the mild, moderate and severe scale

The commonest way of killing in the UK is by asharp instrument. Knight reported in 1975 that it is impossibleto discern with any degree of certainty the degree of force usedto create a stab wound. Despite this, expert witnesses continueto approximate the degree of force used for their reports andevidence in court. It is usually subjectively categorized as mild,moderate or severe, based solely on the examination of thewound. We undertook a study considering forces generated ina range of blunt trauma actions, using a novel force plate dy-namometer to measure the peak forces obtained by adult maleand female volunteers. We then studied forces generated bystabbing skin simulants and porcine samples with knives andscrewdrivers. Men generated more force than women duringstabbings which was found to be equivalent to somewherebetween the blunt trauma actions of pushing a button to asingle-handed push. When asked to stab using what theythought was mild, moderate and severe force, although volun-teers were able to actively decide the force used, the actualforce was found to be influenced by the weapon, sex of theindividual, hand used and biological/anatomical sitepenetrated. This study shows that the forces generated by vol-unteers in mild, moderate and severe stabbing tests in almost allcases were significantly greater than the forces required for skinpenetration. We suggest that the use of subjective force scales isinappropriate. Rather than use of a subjective scale, we suggestthat the force required in any stabbing requires investigation infour areas: the tip radius of the weapon, minimal force requiredfor penetration, the sex of the assailant and whether the forcerequired for penetration is greater than that that can be gener-ated by a person stabbing. This allows for the use of anevidence-based two-tier scale to suggest the force required

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