Sentence:  The <WSD>doctrine of necessity</WSD> might lead a court to approve a doctor′s decision to perform an illegal, third-trimester abortion in order to save the mother′s life. 
Meaning of the word marked with <WSD> tags:  A principle whereby a normally criminal act is justified by the necessity of preserving something of greater utilitarian value than that lost or sacrificed; "not to be confused with self-defence".