duress of circumstance and necessity

• circumstance and necessity


  when d has two alternatives, either commit a crime or suffer

  can't be raised for murder - (Dudley and Stephens)
• three requirements

  act is needed to avoid inevitable and evil

  no more should be done than is reasonably necessary

  the evil inflicted must be proportionate to evil avoided
• defence rarely successful

  driving under influence, defence denied - (kitson)
• generally only successful for medical cases 


  (conjoined twins)