The authors have reported 4 successfully-detected cases of helium in postmortem blood by headspace-gas chromatography (HS-GC). Postmortem blood was collected into a depressurized 4-ml glass vial to prevent volatilization loss of helium. MICROPACKED-ST column (2.0 m×1.0 mm i.d., 80/100 mesh) was used as a separation column, and thermal conductivity detector was selected as a gas chromatographic detector. Argon was used as a carrier gas, and the flow rate was set at 8.3 ml/min. After 0.5 ml air was released into the vial, 0.5 ml headspace gas was manually injected to the instrument. In this analytical condition, helium was well-separated from other gases in the atmosphere. This HS-GC method was applied to real blood samples of 4 suspected cases of helium inhalation, resulting in successful detection of helium in blood in all cases.
  In the case of a suicide by helium inhalation, it is generally difficult to determine the cause of death from an autopsy finding. This case report provides a practical method to obtain direct proof of helium inhalation.