Death caused by a chain saw – homicide, suicide or accident?

Neck injury patterns resulting from the use of petrol and electric chainsaws in suicides. Report on two cases

“…1e8 The application of the guide bar to the neck or lower part of the head produces deep, lethal wounds involving the tegumental areas, muscle, bone, nerves and spinal cord, which cause a rapid demise due to exanguination and collapse due to the interruption of spinal sympathetic fibres. 1,9,10 Analysis of the death scene and related circumstances may sometimes be inconclusive, with forensic investigators having initial difficulty in differentiating between suicide and homicide events. 9 In the event of a chainsaw-related death it is essential that the following steps are taken in order to determine whether a suicide or homicide has been committed: an accurate reconstruction of the event, the scrupulous investigation of the death scene, the reconstruction of the victim's psychiatric history or the prior experience of handling chainsaws or similar tools, and the execution of appropriate autopsy examinations.…”

“…3,9 The main cut is generally straight but may present some tags in the side walls which are extensively contused. 3,9,11 Wound morphology is determined by the shape of the saw teeth whose perpendicular cutting surfaces are designed to cut and remove wood (see Fig. 1).…”

“…1 As a result, the wounded tissue is cut, bruised, chewed and coarsely removed while the margins of the wound may often be contaminated with foreign oily substances, sawdust or wood chips, bark, grease, bacteria or fungal microspores normally lodging on the chain and teeth. 9,11 The teeth's chewing effect produces an accumulation of coarser, heavier fragments of tissue below the cutting attachment while smaller, lighter fragments of tissue and blood are normally launched ahead from the tip of the bar. 12 Schiwy-Bochat et al reported that the saw teeth normally slip off the skin on initial contact with surface tissues but, after increasing manual pressure, the saw penetrates the deeper tissues causing lethal wounds to the deep vessels and nerves of the neck as far as the cervical spine bones.…”

“…3 When the chain hits bone, in the absence of sufficient manual pressure applied by the operator, the dangerous phenomenon known as "kickback" may occur, with the guide bar bouncing back and causing small, secondary, smooth-edged, parallel wounds above the deep primary wound, which may also be enlarged. 9,10,15,16 The wounds caused by kickback may be morphologically different from tentative wounds caused by multiple applications of the bar and may be distant from the main wound and generally less deep.…”

“…However, the edges of a wound caused by a chainsaw are generally more irregular, bruised and ragged when compared with those caused by a steel blade. 9 Autoptic macroscopic and histological confirmation of the vitality of the margins of the main wound are mandatory, in order to exclude the presence of post-mortem cross-cutting wounds on the corpse, inflicted after the subject had been killed by means of a chainsaw or other tools or weapons.…”