Visualisation of contrast-filled stab wounds in various tissue types with computed tomography

Background: Stab wounds are common in homicide cases. Post-mortem multislice computed tomography (PMCT) has proved to be a useful tool in forensic examinations of victims of sharp force trauma, but due the limited resolution of soft tissues, the radiological depiction of a stab channel is difficult. In this study, we have tried to obtain information about the shape of a knife blade by CT scanning contrast-filled experimentally inflicted stab wounds in various types of pig tissue.

Methodology: The tissue samples were mounted on floral foam (oasis) with wooden sticks. Two contrast media were used: one was unmodified and easy flowing, and one was made more viscous with polyethylene glycol. Stab channels in ballistic soap were used for comparison. India ink-filled stab channels were investigated histologically to determine the pattern of leakage.

Principal findings: We found that the shape of the stab wounds on the CT images from lung and muscle tissue did not correspond well to the shape of the inflicting knife. There was a better correspondence in the images obtained from liver, spleen and kidney. The viscous contrast medium was less likely than the thin (easy flowing) contrast medium to spill into to structures outside the stab channel, but some spillage was observed for both types of contrast medium. Air bubbles were only observed in the viscous contrast medium.

Conclusion: Radiological evaluation of a contrast-filled stab wound in isolated tissue blocks did not permit the positive identification of the inflicting weapon, but it was, in tissue blocks from liver, spleen and kidney, possible to obtain a rough idea of the shape of the inflicting knife and to differentiate a knife from a screwdriver.