See criminal law case of E v Dudley & Stevens, Wikipedia link:
http://en.m.wikipedia.org/wiki/R_v_Dudley_and_Stephens
Extract from Wikipedia:
"R v Dudley and Stephens (1884) 14 QBD 273 DC is a leading
Englishcriminal case which established a
precedent, throughout the
common lawworld, that
necessity is not a defence to a charge of
murder. It concerned survival
cannibalism following a
shipwreck and its purported justification on the basis of a
Custom of the Sea.
[1]
Even if thought to be the defence of self defence to the charge of murder (as in, eating this person will save your life, not doing so will kill you), if is NOT ok to kill and eat someone. Also to eat someone who is already dead would be interfering with a corpse, which again is criminal (and rather putrid). Classic criminal law case that challenges one's philosophical understanding of what makes and act criminal and why culpability and vulnerability are significant considerations in deciding what behaviour us criminal and in the sentencing of offenders. For a really good discussion of the case see Mirko Bargaric, Kenneth J Arenson & Peter Gillies' book "Criminal Law in the Common Law Jurisdictions". Fantastic and thought provoking chapters on necessity.